System and method for correcting position errors of a multi-leaf collimator

ABSTRACT

Methods and systems for correcting position errors for a multi-leaf collimator (MLC) are provided. A method may include determining a first position for each of the plurality of leaves. The information associated with the first position may include a first movement direction and a first angle. A movement of the each of the plurality of leaves along the first movement direction may be configured to move toward or away from a center of the radiation field. The method may also include determining an offset value associated with the first position based on the first angle and the first movement direction; and determining a target position of the each of the plurality of leaves based on the offset value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/547,488, filed on Aug. 21, 2019, which claims priority of ChinesePatent Application No. 201810960823.7 filed on Aug. 22, 2018, the entirecontents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure generally relates to a medical treatment systemand more specifically relates to methods and systems for correctingposition errors of one or more leaves of a multi-leaf collimator (MLC)in a radiotherapy procedure.

BACKGROUND

A multi-leaf collimator (MLC) is widely used for collimating radiationbeams emitted from a radiation source in radiotherapy systems. Theradiation beams collimated by an MLC may be projected to the tumor andan area formed by the projected radiation beams may comply with theshape of a tumor to prevent healthy tissues around the tumor from beingradiated. Therefore, the positioning accuracy of the leaves in the MLCis important for precise radiotherapy. At present, the leaves of an MLCare generally driven by motors to move forward or backward to scale aradiation field. In this way, position errors may occur in the movementof the leaves and influence the positioning accuracy of the leaves inthe MLC. It is desirable to provide systems and methods for determiningan offset value of each of the leaves in an MLC for correcting theposition errors.

SUMMARY

According to an aspect of the present disclosure, a method forcorrecting position error of a leaf is provided. The method may beimplemented on at least one machine each of which has at least oneprocessor and storage. The method may include determining a firstposition for each of the plurality of leaves, information associatedwith the first position including a first movement direction and a firstangle, wherein a movement of the each of the plurality of leaves alongthe first movement direction is configured to move toward or away from acenter of the radiation field; determining an offset value associatedwith the first position based on the first angle and the first movementdirection; and determining a target position of the each of theplurality of leaves based on the offset value.

In some embodiments, the determining a first position for each of theplurality of leaves may include obtaining an angle of a gantrycorresponding to the first position of the each of the plurality ofleaves; obtaining an angle of a collimator corresponding to the firstposition of the each of the plurality of leaves, wherein the MLC ismounted in the collimator and rotates along with the collimator; anddetermining the first angle of the each of the plurality of leaves basedon the angle of the gantry and the angle of the collimator.

In some embodiments, the determining a first position for each of theplurality of leaves may include obtaining a first velocity relating tothe driving component; in response to a determination that the firstvelocity relating to the driving component is lower than a firstthreshold, determining the first movement direction as a backwardmovement direction, the each of the plurality of leaves being configuredto move away from the center of the radiation field along the backwardmovement direction; and in response to a determination that the firstvelocity relating to the driving component is greater than a secondthreshold, determining the first movement direction as a forwardmovement direction, the each of the plurality of leaves being configuredto move toward the center of the radiation field along the forwardmovement direction.

In some embodiments, the determining a target position of the each ofthe plurality of leaves based on the offset value may includesubtracting the offset value from a preprogrammed position of the eachof the plurality of leaves.

In some embodiments, the information associated with the first positionmay include a first main encoder value, and the determining an offsetvalue associated with the first position based on the first angle andthe first movement direction may include obtaining a first referenceoffset value associated with the first position of the each of theplurality of leaves from a pre-determined offset table; obtaining afirst main encoder value corresponding to the first position of the eachof the plurality of leaves, the first main encoder value being acquiredby the main encoder; obtaining a second main encoder value correspondingto a second position of the each of the plurality of leaves, the secondmain encoder value being acquired by the main encoder, and the secondposition being a position at where a movement direction of the each ofthe plurality of leaves changes from a second movement direction to thefirst movement direction; and determining the offset value associatedwith the first position based on the first movement direction, the firstreference offset value, and a difference between the first main encodervalue and the second main encoder value.

In some embodiments, the determining the offset value associated withthe first position based on the first movement direction, the firstreference offset value, and a difference between the first main encodervalue and the second main encoder value may include if the each of theplurality of leaves moves away from the center of the radiation fieldalong the first movement direction, designating a minimum value betweenthe first reference offset value and a sum of the difference between thefirst main encoder value and the second main encoder value and a secondreference offset value associated with the second position as the offsetvalue associated with the first position; and if the each of theplurality of leaves moves toward the center of the radiation field alongthe first movement direction, designating a maximum value between thefirst reference offset value and a sum of the second reference offsetvalue associated with the second position and the difference between thefirst main encoder value and the second main encoder value as the offsetvalue associated with the first position.

In some embodiments, the determining an offset value associated with thefirst position based on the first angle and the first movement directionmay include if the each of the plurality of leaves moves toward thecenter of the radiation field along the first movement direction and thefirst angle is equal to 0 degrees, designating the offset valueassociated with the first position as 0.

In some embodiments, the determining a target position of the each ofthe plurality of leaves based on the offset value may include obtaininga first main encoder value corresponding to a first position of each ofthe plurality of leaves acquired by the main encoder; and correcting thefirst main encoder value based on the offset value to obtain the targetposition of the each of the plurality of leaves.

In some embodiments, the correcting the first main encoder value basedon the offset value may include adding the offset value to the firstmain encoder value to obtain the target position of the each of theplurality of leaves.

According to an aspect of the present disclosure, a method forcorrecting position error of a leaf is provided. The method may beimplemented on at least one machine each of which has at least oneprocessor and storage. The method may include determining a firstposition for each of the plurality of leaves, information associatedwith the first position including a first movement phase, wherein amovement of the each of the plurality of leaves moves in the firstmovement phase is configured to move toward or away from a center of theradiation field; determining an offset value associated with the firstposition based on the first movement phase; and determining a targetposition of the each of the plurality of leaves based on the offsetvalue.

According to an aspect of the present disclosure, a system forcorrecting position errors for a multi-leaf collimator (MLC) isprovided. The MLC may include a plurality of leaves to shape a radiationfield, each of the plurality of leaves being associated with a drivingcomponent including a main encoder. The system may include at least onestorage device storing executable instructions, and at least oneprocessor in communication with the at least one storage device, whenexecuting the executable instructions, causing the system to determine afirst position for each of the plurality of leaves, informationassociated with the first position including a first movement directionand a first angle, wherein the each of the plurality of leaves movestoward or away from a center of the radiation field along the firstmovement direction; determine an offset value associated with the firstposition based on the first angle and the first movement direction; anddetermine a target position of the each of the plurality of leaves basedon the offset value.

Additional features will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the artupon examination of the following and the accompanying drawings or maybe learned by production or operation of the examples. The features ofthe present disclosure may be realized and attained by practice or useof various aspects of the methodologies, instrumentalities andcombinations set forth in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplaryembodiments. These exemplary embodiments are described in detail withreference to the drawings. These embodiments are non-limiting exemplaryembodiments, in which like reference numerals represent similarstructures throughout the several views of the drawings, and wherein:

FIG. 1 is a schematic diagram illustrating an exemplary radiotherapysystem according to some embodiments of the present disclosure;

FIG. 2A is a schematic diagram illustrating an exemplary multi-leafcollimator (MLC) according to some embodiments of the presentdisclosure;

FIG. 2B is a schematic diagram illustrating an exemplary control systemof a multi-leaf collimator (MLC) according to some embodiments of thepresent disclosure;

FIG. 2C is a section diagram illustrating an exemplary treatment head ofa radiotherapy device according to some embodiments of the presentdisclosure;

FIG. 3 is a schematic diagram illustrating exemplary hardware and/orsoftware components of an exemplary computing device on which theprocessing device may be implemented according to some embodiments ofthe present disclosure;

FIG. 4 is a schematic diagram illustrating exemplary hardware and/orsoftware components of an exemplary mobile device on which theterminal(s) may be implemented according to some embodiments of thepresent disclosure;

FIG. 5 is a block diagram illustrating an exemplary processing deviceaccording to some embodiments of the present disclosure;

FIG. 6 is a block diagram illustrating an exemplary processing moduleaccording to some embodiments of the present disclosure;

FIG. 7 is a flowchart illustrating an exemplary process for correcting atarget position of a leaf according to some embodiments of the presentdisclosure;

FIG. 8 is a flowchart illustrating an exemplary process for determiningan offset value of a leaf based on the angle of the leaf according tosome embodiments of the present disclosure;

FIG. 9 is a flowchart illustrating another exemplary process fordetermining an offset value of a leaf based on the angle of the leafaccording to some embodiments of the present disclosure;

FIG. 10 is a flowchart illustrating another exemplary process fordetermining a reference offset value of a leaf according to someembodiments of the present disclosure;

FIG. 11 is a schematic diagram illustrating an exemplary movement curveof a leaf according to some embodiments of the present disclosure;

FIG. 12 is a schematic diagram illustrating an exemplary movement curveof a leaf according to some embodiments of the present disclosure;

FIG. 13 is a schematic diagram illustrating another exemplary movementcurve of a leaf according to some embodiments of the present disclosure;

FIG. 14A is a schematic diagram illustrating an exemplary gantry of theradiotherapy device 110 in a sectional view according to someembodiments of the present disclosure;

FIG. 14B-FIG. 14C are schematic diagrams illustrating exemplary leavesof a multi-leaf collimator in a sectional view according to someembodiments of the present disclosure;

FIG. 15 is a schematic diagram illustrating an exemplary relationshipbetween the angle of a leaf and movement curve of the leaf according tosome embodiments of the present disclosure;

FIG. 16 is a schematic diagram illustrating an exemplary movement curveof a leaf according to some embodiments of the present disclosure;

FIG. 17 is a schematic diagram illustrating exemplary movement phases aleaf according to some embodiments of the present disclosure;

FIG. 18A is a schematic illustrating an exemplary angle relationshipbetween a leaf, collimator, and gantry according to some embodiments ofthe present disclosure;

FIG. 18B-18E are schematics illustrating exemplary backlash error of amulti-leaf collimator (MLC) according to some embodiments of the presentdisclosure;

FIG. 19A is a schematic illustrating an exemplary angle relationshipbetween a leaf, collimator, and gantry according to some embodiments ofthe present disclosure; and

FIG. 19B is a graph illustrating an exemplary movement curve of a leafaccording to some embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant disclosure. However, it should be apparent to those skilledin the art that the present disclosure may be practiced without suchdetails. In other instances, well-known methods, procedures, systems,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present disclosure. Various modifications to thedisclosed embodiments will be readily apparent to those skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the spirit and scopeof the present disclosure. Thus, the present disclosure is not limitedto the embodiments shown, but to be accorded the widest scope consistentwith the claims.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise,”“comprises,” and/or “comprising,” “include,” “includes,” and/or“including,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

It will be understood that the term “system,” “engine,” “unit,”“module,” and/or “block” used herein are one method to distinguishdifferent components, elements, parts, section or assembly of differentlevel in ascending order. However, the terms may be displaced by anotherexpression if they achieve the same purpose.

Generally, the word “module,” “unit,” or “block,” as used herein, refersto logic embodied in hardware or firmware, or to a collection ofsoftware instructions. A module, a unit, or a block described herein maybe implemented as software and/or hardware and may be stored in any typeof non-transitory computer-readable medium or another storage device. Insome embodiments, a software module/unit/block may be compiled andlinked into an executable program. It will be appreciated that softwaremodules can be callable from other modules/units/blocks or themselves,and/or may be invoked in response to detected events or interrupts.Software modules/units/blocks configured for execution on computingdevices (e.g., processor 310 as illustrated in FIG. 3 ) may be providedon a computer-readable medium, such as a compact disc, a digital videodisc, a flash drive, a magnetic disc, or any other tangible medium, oras a digital download (and can be originally stored in a compressed orinstallable format that needs installation, decompression, or decryptionprior to execution). Such software code may be stored, partially orfully, on a storage device of the executing computing device, forexecution by the computing device. Software instructions may be embeddedin firmware, such as an EPROM. It will be further appreciated thathardware modules/units/blocks may be included in connected logiccomponents, such as gates and flip-flops, and/or can be included ofprogrammable units, such as programmable gate arrays or processors. Themodules/units/blocks or computing device functionality described hereinmay be implemented as software modules/units/blocks but may berepresented in hardware or firmware. In general, themodules/units/blocks described herein refer to logicalmodules/units/blocks that may be combined with othermodules/units/blocks or divided into sub-modules/sub-units/sub-blocksdespite their physical organization or storage. The description mayapply to a system, an engine, or a portion thereof.

It will be understood that when a unit, engine, module or block isreferred to as being “on,” “connected to,” or “coupled to,” anotherunit, engine, module, or block, it may be directly on, connected orcoupled to, or communicate with the other unit, engine, module, orblock, or an intervening unit, engine, module, or block may be present,unless the context clearly indicates otherwise. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

These and other features, and characteristics of the present disclosure,as well as the methods of operation and functions of the relatedelements of structure and the combination of parts and economies ofmanufacture, may become more apparent upon consideration of thefollowing description with reference to the accompanying drawings, allof which form a part of this disclosure. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not intended to limit thescope of the present disclosure. It is understood that the drawings arenot to scale.

The flowcharts used in the present disclosure illustrate operations thatsystems implement according to some embodiments of the presentdisclosure. It is to be expressly understood, the operations of theflowcharts may be implemented not in order. Conversely, the operationsmay be implemented in inverted order, or simultaneously. Moreover, oneor more other operations may be added to the flowcharts. One or moreoperations may be removed from the flowcharts.

Provided herein are systems and components for medical diagnostic and/ortreatment. In some embodiments, the diagnostic and treatment system mayinclude a radiotherapy system. The radiotherapy system may include atreatment plan system (TPS), an image-guided radiotherapy (IGRT) system,etc. Merely by way of example, the image-guided radiotherapy (IGRT)system may include, for example, a CT guided radiotherapy system, an MRIguided radiotherapy system, etc.

An aspect of the present disclosure relates to a system and method forcorrecting position errors of a multi-leaf collimator (MLC) including aplurality of leaves to scale a radiation field. For each of theplurality of leaves, the system may determine a current position denotedby a first movement direction and a first angle. The movement of each ofthe plurality of leaves along the first movement direction may beconfigured to expand or narrow the radiation field. Then, an offsetvalue associated with the current position of the each of the pluralityof leaves may be determined based on the first angle of the each of theplurality of leaves and the first movement direction of the each of theplurality of leaves. Further, a target position of the each of theplurality of leaves may be determined according to the offset value andthe first movement direction of the leaf.

It should be noted that the radiotherapy system 100 described below ismerely provided for illustration purposes, and not intended to limit thescope of the present disclosure. For persons having ordinary skills inthe art, a certain amount of variations, changes, and/or modificationsmay be deducted under the guidance of the present disclosure. Thosevariations, changes, and/or modifications do not depart from the scopeof the present disclosure.

FIG. 1 is a schematic diagram illustrating an exemplary radiotherapysystem 100 according to some embodiments of the present disclosure. Asshown, the radiotherapy system 100 may include a radiotherapy device110, a processing device 120, storage device 130, one or moreterminal(s) 140, and a network 150. In some embodiments, theradiotherapy device 110, the processing device 120, the storage device130, and/or the terminal(s) 140 may be connected to and/or communicatewith each other via a wireless connection (e.g., the network 150), awired connection, or a combination thereof. The connections between thecomponents in the radiotherapy system 100 may vary. Merely by way ofexample, the radiotherapy device 110 may be connected to the processingdevice 120 through the network 150, as illustrated in FIG. 1 . Asanother example, the radiotherapy device 110 may be connected to theprocessing device 120 directly. As a further example, the storage device130 may be connected to the processing device 120 through the network150, as illustrated in FIG. 1 , or connected to the processing device120 directly. As still a further example, the terminal(s) 140 may beconnected to the processing device 120 through the network 150, asillustrated in FIG. 1 , or connected to the processing device 120directly (as indicated by the bidirectional arrow in the dashed lineshown in FIG. 1 ), or connected to the radiotherapy device 110 directlyor through the network 150. The terminal(s) 140 may be omitted.

The radiotherapy device 110 may perform radiotherapy treatment on atleast one part of a subject. In some embodiments, the radiotherapydevice 110 may include a single modality apparatus, for example, anX-ray therapy apparatus, a Co-60 teletherapy apparatus, a medicalelectron accelerator, etc. In some embodiments, the radiotherapy device110 may be a multi-modality (e.g., two-modality) apparatus to acquire amedical image relating to the at least one part of the subject andperform radiotherapy treatment on the at least one part of the subject.

The subject may be biological or non-biological. For example, thesubject may include a patient, a man-made object, etc. As anotherexample, the subject may include a specific portion, organ, and/ortissue of the patient. For example, the subject may include head, neck,thorax, cardiac, stomach, blood vessel, soft tissue, tumor, nodules, orthe like, or a combination thereof. In some embodiments, the subject mayinclude a region of interest (ROI), such as a tumor, a node, etc.

In some embodiments, the radiotherapy device 110 may include a gantry towhich a treatment head may be connected. The treatment head may includea radiation source 112 and a multi-leaf collimator (MLC) 114. Theradiation source 112 may emit radiation beams to a subject. The MLC 114may be configured to collimate radiation beams emitted from theradiation source 112. In some embodiments, the MLC 114 may include aplurality of leaves to shape a radiation field. The plurality of leavesmay be driven by one or more driving components (e.g., motors) to moveto specific positions to expand or narrow the radiation field. Due tothe mechanical factors associated with the one or more drivingcomponents (e.g., motors), an actual position of a leaf may beinconsistent with an ideal position specified by the processing device120, which causes a position error between the actual position and theideal position. The position error of a leaf may be caused by thebacklash error relating to a driving component, leaf deformation, leafpositioning, horizontality, perpendicularity, or the like, or acombination thereof.

In some embodiments, the driving component may include a main encoderconfigured to acquire a position of a leaf driven by the drivingcomponent. The main encoder may be used to determine the position of theleaf based on a parameter (e.g., a rotation velocity, a rotation count,etc.) of the driving component (e.g., a motor). For example, if thediving component drives a leaf to move via rotations of a motor, themain encoder may be configured to acquire a rotation count of the motor.Then, the position of the leaf may be determined based on the rotationcount of the motor. In some embodiments, the main encoder may include anencoder of the motor (also referred to as motor encoder), apotentiometer mounted on the shaft end of the motor, or any otherposition measurement device. In some embodiments, each of the pluralityof leaves in the MLC 114 may be coupled with an auxiliary encoder. Insome embodiments, the auxiliary encoder may include a grating-ruledisplacement sensor, a Hall sensor, a potentiometer or any otherposition measurement device. More descriptions of the positionmeasurement device may be found, for example, Chinese Application No.201510581866.0, the contents of which are hereby incorporated byreference. More descriptions of the MLC 114 may be found elsewhere inthe present disclosure (e.g., FIG. 2 and the descriptions thereof).

The processing device 120 may process data and/or information obtainedfrom the radiotherapy device 110, the storage device 130, and/or theterminal(s) 140. For example, the processing device 120 may determine amovement direction of a leaf in the MLC 114. As another example, theprocessing device 120 may determine an angle of each of a plurality ofleaves based on an angle of the gantry of the radiotherapy device 110and an angle of a collimator. As a further example, the processingdevice 120 may determine an offset value of each of a plurality ofleaves in the MLC 114, and determine a position of the each of aplurality of leaves in the MLC 114 according to the determined offsetvalue.

In some embodiments, the processing device 120 may be a single server ora server group. The server group may be centralized or distributed. Insome embodiments, the processing device 120 may be local or remote. Forexample, the processing device 120 may access information and/or datafrom the radiotherapy device 110, the storage device 130, and/or theterminal(s) 140 via the network 150. As another example, the processingdevice 120 may be directly connected to the radiotherapy device 110, theterminal(s) 140, and/or the storage device 130 to access informationand/or data. In some embodiments, the processing device 120 may beimplemented on a cloud platform. For example, the cloud platform mayinclude a private cloud, a public cloud, a hybrid cloud, a communitycloud, a distributed cloud, an inter-cloud, a multi-cloud, or the like,or a combination thereof. In some embodiments, the processing device 120may be implemented by a mobile device 400 having one or more componentsas described in connection with FIG. 4 .

The storage device 130 may store data, instructions, and/or any otherinformation. In some embodiments, the storage device 130 may store dataobtained from the radiotherapy device 110, the processing device 120,and/or the terminal(s) 140. In some embodiments, the storage device 130may store data and/or instructions that the processing device 120 mayexecute or use to perform exemplary methods described in the presentdisclosure. In some embodiments, the storage device 130 may include amass storage, removable storage, a volatile read-and-write memory, aread-only memory (ROM), or the like, or any combination thereof.Exemplary mass storage may include a magnetic disk, an optical disk, asolid-state drive, etc. Exemplary removable storage may include a flashdrive, a floppy disk, an optical disk, a memory card, a zip disk, amagnetic tape, etc. Exemplary volatile read-and-write memory may includea random access memory (RAM). Exemplary RAM may include a dynamic RAM(DRAM), a double date rate synchronous dynamic RAM (DDR SDRAM), a staticRAM (SRAM), a thyristor RAM (T-RAM), and a zero-capacitor RAM (Z-RAM),etc. Exemplary ROM may include a mask ROM (MROM), a programmable ROM(PROM), an erasable programmable ROM (EPROM), an electrically erasableprogrammable ROM (EEPROM), a compact disk ROM (CD-ROM), and a digitalversatile disk ROM, etc. In some embodiments, the storage device 130 maybe implemented on a cloud platform as described elsewhere in thedisclosure.

In some embodiments, the storage device 130 may be connected to thenetwork 150 to communicate with one or more other components in theradiotherapy system 100 (e.g., the processing device 120, theterminal(s) 140, etc.). One or more components in the radiotherapysystem 100 may access the data or instructions stored in the storagedevice 130 via the network 150. In some embodiments, the storage device130 may be part of the processing device 120.

The terminal(s) 140 may be connected to and/or communicate with theradiotherapy device 110, the processing device 120, and/or the storagedevice 130. For example, the terminal(s) 140 may obtain a processedimage from the processing device 120. As another example, theterminal(s) 140 may obtain image data acquired via the radiotherapydevice 110 and transmit the image data to the processing device 120 tobe processed. In some embodiments, the terminal(s) 140 may include amobile device 140-1, a tablet computer 140-2, . . . , a laptop computer140-N, or the like, or any combination thereof. For example, the mobiledevice 140-1 may include a mobile phone, a personal digital assistant(PDA), a gaming device, a navigation device, a point of sale (POS)device, a laptop, a tablet computer, a desktop, or the like, or anycombination thereof. In some embodiments, the terminal(s) 140 mayinclude an input device, an output device, etc. The input device mayinclude alphanumeric and other keys that may be input via a keyboard, atouch screen (for example, with haptics or tactile feedback), a speechinput, an eye tracking input, a brain monitoring system, or any othercomparable input mechanism. The input information received through theinput device may be transmitted to the processing device 120 via, forexample, a bus, for further processing. Other types of the input devicemay include a cursor control device, such as a mouse, a trackball, orcursor direction keys, etc. The output device may include a display, aspeaker, a printer, or the like, or a combination thereof. In someembodiments, the terminal(s) 140 may be part of the processing device120.

The network 150 may include any suitable network that can facilitate theexchange of information and/or data for the radiotherapy system 100. Insome embodiments, one or more components of the radiotherapy system 100(e.g., the radiotherapy device 110, the processing device 120, thestorage device 130, the terminal(s) 140, etc.) may communicateinformation and/or data with one or more other components of theradiotherapy system 100 via the network 150. For example, the processingdevice 120 may obtain image data from the radiotherapy device 110 viathe network 150. As another example, the processing device 120 mayobtain user instruction(s) from the terminal(s) 140 via the network 150.The network 150 may be and/or include a public network (e.g., theInternet), a private network (e.g., a local area network (LAN), a widearea network (WAN)), etc.), a wired network (e.g., an Ethernet network),a wireless network (e.g., an 802.11 network, a Wi-Fi network, etc.), acellular network (e.g., a Long Term Evolution (LTE) network), a framerelay network, a virtual private network (VPN), a satellite network, atelephone network, routers, hubs, switches, server computers, and/or anycombination thereof. For example, the network 150 may include a cablenetwork, a wireline network, a fiber-optic network, a telecommunicationsnetwork, an intranet, a wireless local area network (WLAN), ametropolitan area network (MAN), a public telephone switched network(PSTN), a Bluetooth™ network, a ZigBee™ network, a near fieldcommunication (NFC) network, or the like, or any combination thereof. Insome embodiments, the network 150 may include one or more network accesspoints. For example, the network 150 may include wired and/or wirelessnetwork access points such as base stations and/or internet exchangepoints through which one or more components of the radiotherapy system100 may be connected to the network 150 to exchange data and/orinformation.

This description is intended to be illustrative, and not to limit thescope of the present disclosure. Many alternatives, modifications, andvariations will be apparent to those skilled in the art. The features,structures, methods, and other characteristics of the exemplaryembodiments described herein may be combined in various ways to obtainadditional and/or alternative exemplary embodiments. For example, thestorage device 130 may be a data storage including cloud computingplatforms, such as public cloud, private cloud, community, and hybridclouds, etc. As another example, the radiotherapy system 100 may furtherinclude a treatment planning system. However, those variations andmodifications do not depart the scope of the present disclosure.

FIG. 2A is a schematic diagram illustrating an exemplary multi-leafcollimator (MLC) 200 according to some embodiments of the presentdisclosure. As shown in FIG. 2A, the MLC 200 may include a leaf assembly220 including multiple leaves (e.g., a leaf 220-1, a leaf 220-2, a leaf220-i, . . . , a leaf 220-n, etc.), a carriage 240, and a drivingassembly 260. Each of the multiple leaves may move in the carriage 240independently, for example, move toward the center of a radiation fieldor move away from the center of the radiation field. The center of theradiation field may be a geometric center of the radiation field formedby the multiple leaves. The driving assembly 260 may include multiplemotors (e.g., a motor 260-1, a motor 260-2, a motor 260-i, . . . , amotor 260-n, etc.) associated with the multiple leaves (e.g., the leaf220-1, the leaf 220-2, the leaf 220-i, . . . , the leaf 220-n, etc.).Each of the multiple motors (e.g., the motor 260-1, the motor 260-2, themotor 260-i, . . . , the motor 260-n, etc.) may drive a correspondingleaf of the multiple leaves (e.g., the leaf 220-1, the leaf 220-2, theleaf 220-i, . . . , the leaf 220-n, etc.) to move independently in thecarriage 240 to form the radiation field. Each one of the multipleleaves (e.g., the leaf 220-1, the leaf 220-2, the leaf 220-i, . . . ,the leaf 220-n, etc.) may be driven by one of the multiple motors tomove toward the center of the radiation field. Further, each one of themultiple leaves (e.g., the leaf 220-1, the leaf 220-2, the leaf 220-i, .. . , the leaf 220-n, etc.) may be driven by one of the multiple motorsto move away from the center of the radiation field.

FIG. 2B is a schematic diagram illustrating an exemplary control systemof a multi-leaf collimator (MLC) according to some embodiments of thepresent disclosure. As illustrated in FIG. 2B, the control system mayinclude a compensation table module 202, a position controller 204, avelocity controller 206, a velocity feedback module 216, and a positionfeedback module 218.

The position controller 204 may receive a position command associatedwith a preprogrammed position of a leaf 214 and control the velocitycontroller 206 based on the position command. In some embodiments, theposition command associated with the predetermined position of the leaf214 may be modified based on an offset value associated with the leaf214. The offset value associated with the leaf 214 may be determined byand/or obtained from the compensation table module 202 according toprocess 800 as illustrated in FIG. 8 . In some embodiments, the offsetvalue associated with the leaf 214 may be determined based on thecurrent position of the leaf 214 acquired by the position feedbackmodule 218 from an encoder 208 (or a main encoder) and/or a Hall sensor212 (or an auxiliary encoder) according to process 900 as illustrated inFIG. 9 and/or process 1000 as illustrated in FIG. 10 . The velocitycontroller 206 may determine a reference rotation velocity of the motor210 based on the position command. The velocity controller 206 maycontrol the motor 210 to rotate according to the reference rotationvelocity within a certain time to drive the leaf 214 associated with themotor 210 to move to the preprogrammed position. The encoder 208associated with the motor 210 may acquire a rotation count of the motor210 to determine a current or real-time position of the leaf 214. TheHall sensor 212 may be coupled with the leaf 214. The Hall sensor 212may acquire a signal relating to the current or real-time position ofthe leaf 214.

The velocity feedback module 216 may be connected with the encoder 208and/or the Hall sensor 212. The velocity feedback module 216 may beconfigured to determine a current rotation velocity of the motor 210based on the rotation of the motor 210 acquired by the encoder 208.Alternatively or simultaneously, the velocity feedback module 216 may beconfigured to determine a current movement velocity of the leaf 214based on the signal acquired by the Hall sensor 212. The velocitycontroller 206 may acquire the current rotation velocity of the motor210 and/or the current movement velocity of the leaf 214. Then, thevelocity controller 206 may modify the driving force of the motor 210based on a difference between a referenced rotation velocity and thecurrent rotation velocity of the motor 210 and/or a difference between areference velocity and the current movement velocity of the leaf 214.

The position feedback module 218 may be connected to the encoder 208and/or the Hall sensor 212. The position feedback module 218 may beconfigured to determine a current position of the leaf 214 based on therotation count of the motor 210 acquired by the encoder 208 and acurrent movement velocity of the leaf 214 based on magnetic fieldfluctuation signals acquired by the Hall sensor 212 (e.g., an encoder).Then, the position controller 204 may determine an offset valueassociated with the current position of the leaf 214 determined based onthe encoder 208 and/or the Hall sensor 212. The position command may bemodified based on the offset value associated with the current positionof the leaf 214. More descriptions of the MLC may be found, for example,Chinese Publication No. 104667427A entitled “Leaf position monitoringdevice for a multi-leaf collimator (MLC), an MLC, and a radiotherapydevice (

,

,

).”, the contents of which are hereby incorporated by reference.

This description is intended to be illustrative, and not to limit thescope of the present disclosure. Many alternatives, modifications, andvariations will be apparent to those skilled in the art. The features,structures, methods, and other characteristics of the exemplaryembodiments described herein may be combined in various ways to obtainadditional and/or alternative exemplary embodiments. For example, thecompensation table module 202 may be omitted. As another example, thevelocity feedback module 216 and the position feedback module 218 may beintegrated into one single module. However, those variations andmodifications do not depart the scope of the present disclosure.

FIG. 2C is a section diagram illustrating an exemplary treatment head ofa radiotherapy device according to some embodiments of the presentdisclosure. As illustrated in FIG. 2C, the treatment head may include aradiation source 230, a primary collimator 250, one or more filters 252,a collimator 290, or any other component (e.g., a chamber between theone or more filters 252 and the collimator 290). The radiation source230 may generate and/or emit radiation beams to a subject. The radiationsource may include an accelerator 232, a target 234, or any othercomponent (not shown). The primary collimator 250 may be configured tolimit or collimate high energy beams (e.g., X-rays) emitted from theradiation source so that only those traveling parallel to a specifieddirection are allowed to pass through the primary collimator 250. Theone or more filters 252 may be configured to adjust the distribution ofthe radiation impinging upon the subject. The one or more filters 252may include a flattening filter, a bowtie filter, a wedge filter, or thelike, or any combination thereof.

The collimator 290 may be configured to shape a radiation field. Thecollimator 290 may include a Y-JAW 291, a X-JAW 292, an MLC 293including a leaf assembly 2931 and a carriage 2934, or any othercomponents. The leaf assembly 2933 may include multiple leaves. The MLC293 may also include a driving assembly (not shown). Each of themultiple leaves may move in the carriage 2934 independently, forexample, move toward the center of a radiation field or move away fromthe center of the radiation field to shape the radiation field. The MLC293, the Y-JAW 291, and the X-JAW 292 may be form the radiation field,cooperatively. The MLC 293 may be mounted in the collimator 290. Thecollimator 290 may rotate. The MLC 293 may rotate along the rotation ofthe collimator 290. More descriptions for the MLC 293 may be found inelsewhere in the present disclosure (e.g., FIG. 2A and the descriptionsthereof).

FIG. 3 is a schematic diagram illustrating exemplary hardware and/orsoftware components of an exemplary computing device 300 on which theprocessing device 120 may be implemented according to some embodimentsof the present disclosure. As illustrated in FIG. 3 , the computingdevice 300 may include a processor 310, storage 320, an input/output(I/O) 330, and a communication port 340.

The processor 310 may execute computer instructions (e.g., program code)and perform functions of the processing device 120 in accordance withtechniques described herein. The computer instructions may include, forexample, routines, programs, objects, components, data structures,procedures, modules, and functions, which perform particular functionsdescribed herein. For example, the processor 310 may process dataobtained from the radiotherapy device 110, the storage device 130,terminal(s) 140, and/or any other component of the radiotherapy system100. In some embodiments, the processor 310 may include one or morehardware processors, such as a microcontroller, a microprocessor, areduced instruction set computer (RISC), an application specificintegrated circuits (ASICs), an application-specific instruction-setprocessor (ASIP), a central processing unit (CPU), a graphics processingunit (GPU), a physics processing unit (PPU), a microcontroller unit, adigital signal processor (DSP), a field programmable gate array (FPGA),an advanced RISC machine (ARM), a programmable logic device (PLD), anycircuit or processor capable of executing one or more functions, or thelike, or a combinations thereof.

Merely for illustration, only one processor is described in thecomputing device 300. However, it should be noted that the computingdevice 300 in the present disclosure may also include multipleprocessors. Thus operations and/or method steps that are performed byone processor as described in the present disclosure may also be jointlyor separately performed by the multiple processors. For example, if inthe present disclosure the processor of the computing device 300executes both operations A and B, it should be understood that operationA and operation B may also be performed by two or more differentprocessors jointly or separately in the computing device 300 (e.g., afirst processor executes operation A and a second processor executesoperation B, or the first and second processors jointly executeoperations A and B).

The storage 320 may store data/information obtained from theradiotherapy device 110, the storage device 130, the terminal(s) 140,and/or any other component of the radiotherapy system 100. In someembodiments, the storage 320 may include a mass storage, removablestorage, a volatile read-and-write memory, a read-only memory (ROM), orthe like, or a combination thereof. For example, the mass storage mayinclude a magnetic disk, an optical disk, a solid-state drive, etc. Theremovable storage may include a flash drive, a floppy disk, an opticaldisk, a memory card, a zip disk, a magnetic tape, etc. The volatileread-and-write memory may include a random access memory (RAM). The RAMmay include a dynamic RAM (DRAM), a double date rate synchronous dynamicRAM (DDR SDRAM), a static RAM (SRAM), a thyristor RAM (T-RAM), and azero-capacitor RAM (Z-RAM), etc. The ROM may include a mask ROM (MROM),a programmable ROM (PROM), an erasable programmable ROM (EPROM), anelectrically erasable programmable ROM (EEPROM), a compact disk ROM(CD-ROM), and a digital versatile disk ROM, etc. In some embodiments,the storage 320 may store one or more programs and/or instructions toperform exemplary methods described in the present disclosure.

The I/O 330 may input and/or output signals, data, information, etc. Insome embodiments, the I/O 330 may enable user interaction with theprocessing device 120. In some embodiments, the I/O 330 may include aninput device and an output device. Examples of the input device mayinclude a keyboard, a mouse, a touch screen, a microphone, or the like,or a combination thereof. Examples of the output device may include adisplay device, a loudspeaker, a printer, a projector, or the like, or acombination thereof. Examples of the display device may include a liquidcrystal display (LCD), a light-emitting diode (LED)-based display, aflat panel display, a curved screen, a television device, a cathode raytube (CRT), a touch screen, or the like, or a combination thereof.

The communication port 340 may be connected to a network (e.g., thenetwork 150) to facilitate data communications. The communication port340 may establish connections between the processing device 120 and theradiotherapy device 110, the storage device 130, and/or the terminal(s)140. The connection may be a wired connection, a wireless connection,any other communication connection that can enable data transmissionand/or reception, and/or a combination of these connections. The wiredconnection may include, for example, an electrical cable, an opticalcable, a telephone wire, or the like, or a combination thereof. Thewireless connection may include, for example, a Bluetooth™ link, aWi-Fi™ link, a WiMax™ link, a WLAN link, a ZigBee link, a mobile networklink (e.g., 3G, 4G, 5G, etc.), or the like, or a combination thereof. Insome embodiments, the communication port 340 may be and/or include astandardized communication port, such as RS232, RS485, etc. In someembodiments, the communication port 340 may be a specially designedcommunication port. For example, the communication port 340 may bedesigned in accordance with the digital imaging and communications inmedicine (DICOM) protocol.

FIG. 4 is a schematic diagram illustrating exemplary hardware and/orsoftware components of an exemplary mobile device 400 on which theterminal(s) 140 may be implemented according to some embodiments of thepresent disclosure. As illustrated in FIG. 4 , the mobile device 400 mayinclude a communication platform 410, a display 420, a graphicsprocessing unit (GPU) 430, a central processing unit (CPU) 440, an I/O450, a memory 460, and a storage 490. In some embodiments, any othersuitable component, including but not limited to a system bus or acontroller (not shown), may also be included in the mobile device 400.In some embodiments, a mobile operating system 470 (e.g., iOS™,Android™, Windows Phone™, etc.) and one or more applications 480 may beloaded into the memory 460 from the storage 490 in order to be executedby the CPU 440. The applications 480 may include a browser or any othersuitable mobile apps for receiving and rendering information relating toimage processing or other information from the processing device 120.User interactions with the information stream may be achieved via theI/O 450 and provided to the processing device 120 and/or othercomponents of the radiotherapy system 100 via the network 150.

To implement various modules, units, and their functionalities describedin the present disclosure, computer hardware platforms may be used asthe hardware platform(s) for one or more of the elements describedherein. A computer with user interface elements may be used to implementa personal computer (PC) or any other type of work station or terminaldevice. A computer may also act as a server if appropriately programmed.

FIG. 5 is a block diagram illustrating an exemplary processing device120 according to some embodiments of the present disclosure. Theprocessing device 120 may include an acquisition module 502, a controlmodule 504, a processing module 506, and a storage module 508. At leasta portion of the processing device 120 may be implemented on a computingdevice as illustrated in FIG. 3 or a mobile device as illustrated inFIG. 4 .

The acquisition module 502 may acquire data. In some embodiments, thedata may be acquired from the radiotherapy device 110, the storagedevice 130, and/or the terminal(s) 140. In some embodiments, the datamay include parameters (e.g., an angle) relating to an MLC, movementinformation (e.g., movement directions, movement phases, etc.) relatingto a leaf in an MLC, an offset table associated with an MLC,instructions, or the like, or a combination thereof. The instructionsmay be executed by the processor(s) of the processing device 120 toperform exemplary methods described in the present disclosure. In someembodiments, the acquired data may be transmitted to the processingmodule 506 for further processing, or stored in the storage module 508.

The control module 504 may control operations of the acquisition module502, the processing module 506, and/or the storage module 508, forexample, by generating one or more control parameters. For example, thecontrol module 504 may control the acquisition module 502 to acquiredata (e.g., an angle of an MLC, an angle of a gantry, etc.). As anotherexample, the control module 504 may control the processing module 506 togenerate an image relating to a subject. As a further example, thecontrol module 504 may control the processing module 506 to implement aradiotherapy treatment plan for the subject. In some embodiments, thecontrol module 504 may receive a real-time command or retrieve apreprogrammed command provided by a user (e.g., a doctor) to control oneor more operations of the acquisition module 502 and/or the processingmodule 506. For example, the control module 504 may adjust theacquisition module 502 and/or the processing module 506 to determine theangle of a leaf according to the real-time command and/or thepreprogrammed command. In some embodiments, the control module 504 maycommunicate with one or more other modules of the processing device 120for exchanging information and/or data.

The processing module 506 may process data provided by various modulesof the processing device 120. For example, the processing module 506 maydetermine an offset value for each of leaves in a collimator (e.g., amulti-collimator in the radiotherapy device 110). As another example,the processing module 506 may generate a position instruction based onthe offset value for each of the leaves in the collimator (e.g., amulti-leaf collimator in the radiotherapy device 110).

The storage module 508 may store information. The information mayinclude programs, software, algorithms, data, text, number, images, andsome other information. For example, the information may include imagedata (e.g., a radiological image, an optical image, etc.), motion orposition data (e.g., a speed, a displacement, an acceleration, a spatialposition, etc.) relating to a component in the radiotherapy device 110(e.g., the couch), instructions, or the like, or a combination thereof.In some embodiments, the storage module 508 may store program(s) and/orinstruction(s) that can be executed by the processor(s) of theprocessing device 120 to acquire data, determine a spatial position ofat least one part of a subject.

In some embodiments, one or more modules illustrated in FIG. 5 may beimplemented in at least part of the radiotherapy system 100 asillustrated in FIG. 1 . For example, the acquisition module 502, thecontrol module 504, the processing module 506, and/or the storage module508 may be integrated into a console (not shown). Via the console, auser may set parameters for scanning a subject, controlling imaging ortreatment processes, controlling parameters for the reconstruction of animage, etc. In some embodiments, the console may be implemented via theprocessing device 120 and/or the terminal(s) 140.

FIG. 6 is a block diagram illustrating an exemplary processing module506 according to some embodiments of the present disclosure. Theprocessing module 506 may include a movement determination unit 602, anangle determination unit 604, an offset determination unit 606, aposition adjustment unit 608, and a storage unit 610. At least a portionof the processing module 506 may be implemented on a computing device asillustrated in FIG. 3 or a mobile device as illustrated in FIG. 4 .

The movement determination unit 602 may be configured to determine amovement direction or a movement phase of the leaf. In some embodiments,the movement determination unit 602 may determine the movement directionor movement phase of the leaf based on the measurements of a mainencoder (e.g., a motor encoder) connected with a driving componentand/or an auxiliary encoder (e.g., a Hall sensor) associated with theleaf. For example, when an initial phase is an unknown phase, and themovement determination unit 602 may obtain a first measurement value anda second measurement value of the leaf through the Hall sensor in twoadjacent sampling periods. If the difference between the firstmeasurement value and the second measurement value is larger than afirst preprogrammed count (e.g., 2 count, etc.), the leaf may bedetermined in a forward movement phase. If the difference between thefirst measurement value and the second measurement value is less than asecond preprogrammed count (e.g., 0 count, etc.), then the leaf may bedetermined in a backward movement phase. In some embodiments, themovement determination unit 602 may be configured to determine amovement direction or a movement phase of the leaf based on a velocityof the leaf and/or a driving component associated with the leaf. Forexample, if the velocity of the driving component is less than avelocity threshold, the leaf may move away from the center of aradiation field.

The angle determination unit 604 may be configured to determine an angleof the leaf. In some embodiments, the angle of the leaf may bedetermined by the angle determination unit 604 based on an angle of thegantry and an angle of a collimator. The collimator may be configured tosupport the MLC. More descriptions of the determining the angle of theleaf based on the angle of the gantry and the angle of the collimatormay be found in operation 704 and the descriptions thereof.

The offset determination unit 606 may be configured to determine thetarget offset of the leaf. In some embodiments, the offset determinationunit 606 may determine the offset value of the leaf based on apreprogrammed offset table. In some embodiments, the offset value of theleaf may be determined based on measurement values acquired by a mainencoder of a driving component associated with the leaf and an auxiliaryencoder associated with the leaf.

The position adjustment unit 608 may be configured to adjust theposition of the leaf. In some embodiments, the position adjustment unit608 may determine a target position of the leaf based on the offsetvalue determined by the offset determination unit 606 associated withthe position of the leaf. Further, the target position of the leaf maybe determined by subtracting the offset value from a preprogrammedposition of the leaf. The preprogrammed position of the leaf may be setby a user via the terminal device 140, or according to a default settingof the radiotherapy system 100, such as a treatment plan of a subject.In some embodiments, the position adjustment unit 608 may determine anactual position of the leaf based on the offset value determined by theoffset determination unit 606 associated with the position of the leaf.Further, the actual position of the leaf based on the offset valuedetermined by summing the current position of the leaf and the offsetvalue. The current position of the leaf may be determined using the mainencoder.

The storage unit 610 may store information relating to, for example,determining the reference offset value, adjusting the position of theleaf, etc. The information may include programs, software, algorithms,data, text, number, and some other information. In some embodiments, theinformation relating to determining the reference offset may includedata for determining the reference offset, algorithms for determiningthe reference offset value, parameters for determining the referenceoffset value, etc. The storage unit 610 may be a memory that stores datato be processed by processing devices, such as CPUs, GPUs, etc. In someembodiments, the storage unit 610 may be a memory that may be accessibleby one or more GPUs or maybe a memory that is only accessible by aspecific GPU.

It should be noted that the above description of the processing module506 is merely provided for the purposes of illustration, and notintended to limit the scope of the present disclosure. For personshaving ordinary skills in the art, multiple variations or modificationsmay be made under the teachings of the present disclosure. However,those variations and modifications do not depart from the scope of thepresent disclosure. For example, the movement determination unit 602 andthe angle determination unit 604 may be integrated into one single unit.

FIG. 7 is a flowchart illustrating an exemplary process 700 fordetermining a target position of a leaf according to some embodiments ofthe present disclosure. In some embodiments, one or more operations ofprocess 700 illustrated in FIG. 7 may be implemented in the radiotherapysystem 100 illustrated in FIG. 1 . For example, the process 700illustrated in FIG. 7 may be stored in the storage device 130 in theform of instructions, and invoked and/or executed by the processingdevice 120 (e.g., the processor 310 of the computing device 300 asillustrated in FIG. 3 , the GPU 430 or CPU 440 of the mobile device 400as illustrated in FIG. 4 ).

In 702, a movement direction of a leaf corresponding to a currentposition of the leaf in a multi-leaf collimator (MLC) may be determined.Operation 702 may be performed by the processing module 506. As usedherein, the current position may be also referred to as a firstposition. In some embodiments, the movement direction of the leaf mayinclude one of a backward movement direction and a forward movementdirection. As used herein, the movement direction of a leaf may beconsidered as the backward movement direction if the leaf moves awayfrom the center of a radiation field. The movement direction of a leafmay be considered to as the forward movement direction if the leaf movestoward the radiation field. In some embodiments, the movement directionof the leaf may correspond to a current or real-time movement directionwhen the leaf is at the current position. In some embodiments, themovement direction of the leaf may correspond to a preprogrammedmovement direction of the leaf. The preprogrammed movement direction ofthe leaf may be determined based on an initial position of the leaf anda preprogrammed position of the leaf in a radiotherapy planningassociated with the MLC. As used herein, the preprogrammed position ofthe leaf may refer to a default (or a commanded) position defined by amain encoder in the driving component. The preprogrammed position of theleaf may be set by a user via the terminal device 140, or according to adefault setting of the radiotherapy system 100, such as a treatment planassociated with the MLC.

In some embodiments, the movement direction of the leaf may bedetermined based on a rotation direction of a motor associated with theleaf in the driving component of the MLC. In some embodiments, therotation direction of the motor may include one of a first rotationdirection and a second rotation direction. When the motor rotates withthe first rotation direction (e.g., a clockwise direction oranti-clockwise direction), the rotation of the motor may cause the leafto move away from the center of the radiation field (i.e., with thebackward movement direction). When the motor rotates with the secondrotation direction (e.g., a clockwise direction or anti-clockwisedirection), the rotation of the motor may cause the leaf to move towardthe center of the radiation field (i.e., with the forward movementdirection).

In some embodiments, the rotation direction of the motor may bedetermined based on a rotation velocity of the motor when the leaf is atthe current position. Further, if the rotation velocity of the motor isless than a first velocity threshold, the rotation direction of themotor may be determined as the first rotation direction. If the rotationvelocity of the motor is greater than a second velocity threshold, therotation direction of the motor may be determined as the second rotationdirection. In some embodiments, the rotation velocity of the motor maybe preprogrammed based on the preprogrammed position of the leaf. Insome embodiments, the rotation velocity of the motor may be a current orreal-time rotation velocity determined based on an encoder valueacquired by a main encoder associated with the motor when the leaf is atthe current position. For example, in adjacent sampling periods (alsoreferred to as adjacent calculation cycles) of the main encoder, twomeasurements may be acquired by the main encoder corresponding twodifferent positions of the leaf. The rotation velocity of the motor maybe determined based on the two measurements and the sampling period.

In some embodiments, the rotation direction of the motor may bedetermined based on the preprogrammed position of the leaf and thecurrent position of the leaf. For example, if a distance between thepreprogrammed position of the leaf and a reference point (e.g., thefront end A of the MLC 200 as shown in FIG. 2A) is greater than adistance between the current position of the leaf and the referencepoint, the rotation direction of the motor may cause the leaf to movetoward the preprogrammed position, i.e., move toward the center of theradiation field. If the distance between the preprogrammed position ofthe leaf and the reference point is less than the distance between thecurrent position of the leaf and the reference point, the rotationdirection of the motor may cause the leaf to move toward thepreprogrammed position, i.e., move away from the center of the radiationfield. The first velocity threshold may be a constant lower than orequal to zero, and the second velocity threshold may be a constant equalto or greater than zero. The first velocity threshold and/or the secondvelocity threshold may be determined by a user or according to a defaultsetting of the radiotherapy system 100.

In 704, an angle of the leaf corresponding to the current position ofthe leaf may be determined. Operation 704 may be performed by the angledetermination unit 604. The angle of the leaf may be determined based onan angle of a collimator for supporting the MLC (e.g., the MLC 114) andan angle of a gantry of a radiotherapy device (e.g., the radiotherapydevice 110) including the MLC. The MLC may be mounted on the collimatorand rotate with the collimator. Further, the angle of the leaf may bedetermined according to Equation (1) as described below:sin(α)=sin(β)*cos(θ)  (1)where, α represents an angle of a leaf; β represents an angle of agantry of a radiotherapy device, and θ represents an angle of acollimator in the gantry of the radiotherapy device. As used herein, anangle of a leaf, an angle of a gantry of a radiotherapy device, and anangle of a collimator may be described in the coordinate systems of IEC(International Electrotechnical Commission) specifications.

According to Equation (1), when the angle of the gantry is 0 degrees andthe angle of the collimator is 90 degrees, the angle of the leaf may bedetermined to be 0 degrees. When the angle of the gantry is 90 degreesand the angle of the collimator is 0 degrees, the angle of the leaf maybe determined to be 90 degrees. When the angle of the gantry is 45degrees and the angle of the collimator is 45 degrees, the angle of theleaf may be determined to be 30 degrees. In some embodiments, the angleof the gantry and the angle of the MLC may be determined according to adefault setting of the radiotherapy system 100, such as a treatmentplanning associated with the radiotherapy system 100. In someembodiments, the angle of the gantry and the angle of the collimator maybe obtained from a control system associated with the collimator. Insome embodiments, the angle of the gantry and the angle of thecollimator may be determined using a measurement device, for example, anangle sensor associated with the gantry and/or the collimator.

In 706, an offset value of the leaf may be determined based on the angleof the leaf and the movement direction of the leaf. Operation 706 may beperformed by the offset determination unit 606. In some embodiments, areference offset value of the leaf may be determined based on the angleof the leaf and the movement direction of the leaf. The offset value ofthe leaf may be determined based on a reference offset value. Thereference offset value may obtain from an offset table (e.g., the OffsetTable 1 as described in FIG. 8 ) associated with the MLC. In someembodiments, the offset table may include a plurality of referenceoffset values associated with each of a plurality of leaves underdifferent angles and/or different movement directions. For example, eachof the plurality of reference offset values of each of the plurality ofleaves may be determined based on angles and movement directions of eachof the plurality of leaves in the MLC using a distance measurementdevice and a main encoder of the driving component (e.g., a motor)associated with the each of the plurality of leaves. The distancemeasurement device may include a laser sensor, a dial indicator, adial-gauge, etc. In some embodiments, the offset table may include aplurality of reference offset values associated with each of a pluralityof leaves under different angles, different movement directions, anddifferent positions. For example, each of the plurality of referenceoffset values may be determined based on angles, movement directions,and/or positions of each of a plurality of leaves in the MLC using alaser sensor and a main encoder of the driving component (e.g., a motor)associated with the each of the plurality of leaves. A reference offsetvalue corresponding to the leaf may be determined from the offset tableaccording to the movement direction of the leaf determined in 702, theangle of the leaf determined in 704, and/or the current position of theleaf described in 702. Then, the offset value of the leaf may bedetermined based on the reference offset value corresponding to theleaf. More descriptions for determining the offset value of the leafbased on the offset table may be found in FIG. 8 , and the descriptionsthereof.

In some embodiments, the offset value of the leaf may be determinedbased on a movement phase of the leaf. In some embodiments, a currentmovement phase of the leaf may be determined based on measurement valuesof the main encoder (e.g., a motor encoder) of the driving componentand/or the auxiliary encoder (e.g., a Hall sensor) associated with theleaf. The current movement phase of the leaf may be also referred to asa first movement phase. The offset value of the leaf may be determinedbased on the current movement phase of the leaf. For example, thecurrent position of the leaf as described in 702 may be denoted by afirst main encoder value acquired by the main encoder. A phasetransition position of the leaf at where the leaf moves from a priormovement phase to the current movement phase may be denoted by a secondmain encoder value acquired by the main encoder. The offset value of theleaf may be determined based on a difference between the first mainencoder value and the second main encoder value and a reference offsetvalue associated with the phase transition position of the leaf. In someembodiments, the offset value of the leaf may be determined based on thecurrent angle of the leaf and the current movement phase of the leaf.More descriptions for determining the offset value of the leaf based onthe movement phase of the leaf may be found in FIGS. 9-11 and thedescriptions thereof.

In 708, a target position of the leaf may be determined based on theoffset value. Operation 708 may be performed by the position adjustmentunit 608. As used herein, the target position may be denoted by a mainencoder value of the main encoder of the driving component associatedwith leaf. In some embodiments, the target position may refer to aposition determined by calibrating, based on the offset value, thepreprogrammed position of the leaf as described in 702. For example, theposition adjustment unit 608 may adjust the preprogrammed position ofthe leaf based on the offset value associated with the current positionof the leaf to obtain the target position of the leaf. Further, thetarget position of the leaf may be determined by subtracting the offsetvalue from the preprogrammed position of the leaf. For example, the leafis at the current position of 10 millimeters from the reference point(e.g., the front end A of the MLC 200 as shown in FIG. 2A) and in aforward movement direction, and the preprogrammed position of the leafis 50 millimeter from the reference point. If the offset value of theleaf associated with the current position of 10 millimeters from thereference point determined in 706 is −2 millimeter, then the targetposition of the leaf may be a difference of the preprogrammed positionand the offset value, which is equal to 52 millimeters. The motor mayrotate in the second rotation direction to cause the leaf to move in theforward movement direction to the position of 50 millimeters from thereference point. As another example, the leaf is at the current positionof 50 millimeters from the reference point and in a backward movementdirection, and the preprogrammed position of the leaf is 20 millimeterfrom the reference point. If the offset value of the leaf associatedwith the current position of 50 millimeters from the reference pointdetermined in 706 is 1.5 millimeter, then the target position of theleaf may be a difference between the preprogrammed position and theoffset value, which is equal to 18.5 millimeters. The motor may rotatein the first rotation direction to cause the leaf to move in thebackward movement direction to the position of 20 millimeters from thereference point.

In some embodiments, an actual position (i.e., the target position) ofthe leaf corresponding to the current position of the leaf may bedetermined based on the offset value of the leaf. The target positioncorresponding to the current position may refer to a position determinedby calibrating the current position based on the offset value. Forexample, the position adjustment unit 608 may adjust the currentposition of the leaf based on the offset value to obtain the targetposition (i.e., the actual position) of the leaf. Further, the targetposition (i.e., the actual position) of the leaf corresponding to thecurrent position may be determined by summing the offset value and thecurrent position of the leaf acquired by the main encoder. For example,the leaf is at the current position of 10 millimeters from the referencepoint (e.g., the front end A of the MLC 200 as shown in FIG. 2A) and inthe forward movement direction. If the offset value of the leafassociated with the current position of 10 millimeters determined in 706is −2 millimeter, then the target position (i.e., the actual position)of the leaf may be a sum of the current position and the offset value,which is equal to 8 millimeters. As another example, the leaf is at thecurrent position of 50 millimeters from the reference point in thebackward movement direction. If the offset value of the leaf associatedwith the current position of 50 millimeters determined in 706 is 1.5millimeter, then the target position (i.e., the actual position) of theleaf may be a sum between the current position and the offset value,which is equal to 51.5 millimeters.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations or modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. For example,operation 706 may be divided into at least two operations. Operations702 and 704 may be performed simultaneously. Further, a current positionof a leaf may be determined. The current position of the leaf may bedenoted by the movement direction of the leaf and the angle of the leaf.

FIG. 8 is a flowchart illustrating an exemplary process 800 fordetermining an offset value of a leaf based on the angle of the leaf anda movement direction of the leaf according to some embodiments of thepresent disclosure. In some embodiments, one or more operations ofprocess 800 illustrated in FIG. 8 may be implemented in the radiotherapysystem 100 illustrated in FIG. 1 . For example, process 800 illustratedin FIG. 8 may be stored in the storage device 130 in the form ofinstructions, and invoked and/or executed by the processing device 120(e.g., the processor 310 of the computing device 300 as illustrated inFIG. 3 , the GPU 430 or CPU 440 of the mobile device 400 as illustratedin FIG. 4 ). Operation 706 may be performed according to process 800.

In 802, a first reference offset value of a leaf associated with acurrent position of the leaf may be obtained based on a movementdirection and an angle of the leaf. Operation 802 may be performed bythe acquisition module 502. The movement direction of the motor and theangle of the leaf may be determined as described in connection withoperations 702 and 704 in FIG. 7 .

In some embodiments, the first reference offset value of the leaf may bedetermined from an offset table (e.g., Offset Table 1 as shown below)associated with an MLC including the leaf based on the movementdirection of the leaf and the angle of the leaf. The offset table (e.g.,Offset Table 1 as shown below) may include a plurality of referenceoffset values. Each of the plurality of reference offset values maycorrespond to one of a plurality of leaves in the MLC (e.g., the MLC 114as shown in FIG. 1 ) under a specific angle and a specific movementdirection. In some embodiments, the offset table of the MLC may bedetermined by and/or stored in the radiotherapy system 100. Theacquisition module 502 may obtain the reference offset value of the leafand/or the offset table of the MLC from the storage device 130, thestorage 320, the storage 490, the storage module 508, the storage unit610, and/or any other external storage.

In some embodiments, one of the plurality of reference offset values inthe offset table associated with one of the plurality of leaves in theMLC may be determined using a distance measurement device and a mainencoder of a driving component (e.g., a motor) when the one of theplurality of leaves is moving in a specific movement direction (e.g.,the forward movement direction or the backward movement direction) undera specific angle (e.g., 0 degrees, 45 degrees, 90 degrees, etc.). Themain encoder of the driving component (e.g., a motor) associated withthe one of the plurality of leaves may be configured to acquire theposition of the one of the plurality of leaves that may be inaccuratecaused by a position error (e.g., the backlash error) as describedelsewhere in the present disclosure. The distance measurement device maybe configured to acquire an exact position of one or more of theplurality of leaves. The position (i.e., inaccurate position) of a leafacquired by the main encoder of the driving component of the leaf may beinaccurate with respect to the position (i.e., exact position) of theleaf acquired by the distance measurement device. Further, the one ofthe plurality of reference offset values of the one of the plurality ofleaves may be determined based on a difference between the exactposition and the inaccurate position of the one of the plurality ofleaves.

As shown in Offset Table 1, an MLC may include 120 leaves. Each of theplurality of leaves may have a specific leaf ID. Each of the pluralityof leaves in the MLC may correspond to different reference offset valuesunder different angles and different movement directions (e.g., theforward movement direction or backward movement direction shown inOffset Table 1). The angle of each of the plurality of leaves may be ina range from −90 degrees to 90 degrees. As used herein, the angle of aleaf is 0 degree if the leaf and a driving component (e.g., a motor)associated with the leaf are both parallel to the horizontal plane. Theangle of a leaf is less than 0 degree if the leaf is located above adriving component (e.g., a motor) associated with the leaf. The angle ofa leaf is greater than 0 degrees if the leaf is located below a drivingcomponent (e.g., a motor) associated with the leaf. In some embodiments,reference offset values of a specific leaf may be measured under aseries of coherent angle values (e.g., every 10 degrees) between −90degrees to 90 degrees. In some embodiments, reference offset values of aspecific leaf may be measured under a series of distributed and randomangle values (e.g., 10 degrees, 5 degrees, 2 degrees, etc.). As shown inOffset Table 1, the offset value is measured every 10 degrees of theleaf angle. And with a specific degree of the leaf, reference offsetvalues of the specific leaf is measured in two different movementdirections, the forward movement direction (i.e. Forward in OffsetTable 1) and the backward movement direction (i.e. Backward in OffsetTable 1).

OFFSET TABLE 1 Leaf ID Leaf angle Leaf ID 1 . . . 60 . . . 120  90Forward Backward  80 Forward Backward . . .   0 Forward Backward . . .−80 Forward Backward −90 Forward Backward

In some embodiments, a relationship between the reference offset valueand the current position of a specific leaf in the MLC may be furtherdetermined when the leaf with a specific angle is moving at a specificdirection. For example, when the leaf with the specific angle is movingat the specific movement direction, multiple positions of the specificleaf may be acquired using the distance measurement device and the mainencoder of a driving component (e.g., a motor) respectively. Each of themultiple positions may be denoted by a main encoder value acquired bythe main encoder and a measurement value acquired by the distancemeasurement device. Each of multiple reference offset values associatedwith the each of the multiple positions of the specific leaf may bedetermined based on a difference between the main encoder value acquiredby the main encoder and the measurement value acquired by the distancemeasurement device. The relationship between the reference offset valueand the position of the specific leaf when the leaf with the specificangle is moving at the specific direction may be determined based on themultiple reference offset values and the multiple positions using, forexample, a polynomial fitting technique (e.g., a binomial fittingalgorithm). Then, the reference offset value of the leaf associated withthe current position may be determined based on the current position andthe relationship between the reference offset value and the position ofthe leaf corresponding to the movement direction and the angle. In someembodiments, the offset table may include multiple relationships betweenthe reference offset value and the position of each of the plurality ofleaves under different angles and movement directions. In someembodiments, the offset table may include multiple reference offsetvalues of each of the plurality of leaves under different angles,different movement directions, and different positions. A currentreference offset value of a leaf corresponding to the current positionmay be obtained from the offset table based on the current position ofthe leaf, the angle of the leaf and the movement direction of the leaf.

In 804, a first main encoder value acquired by a main encoder of adriving component associated with leaf may be obtained, which may beassociated with the current position of the leaf. The operation 804 maybe performed by the acquisition module 502. The first main encoder valuemay represent the current position of the leaf. In some embodiments, thefirst main encoder value may be obtained from the MLC 114, the storagedevice 130, the storage module 508, the storage unit 610, or any otherexternal storage.

In 806, a second main encoder value acquired by the main encoder of thedriving component associated with the leaf may be obtained, which may beassociated with a prior position of the leaf when a movement directionof the leaf (or a rotation direction of the motor) changes. Operation806 may be performed by the acquisition module 502. The second mainencoder value may represent the prior position of the leaf. As usedherein, the prior position of the leaf may be also referred to as adirection transition position of the leaf. In some embodiments, when theleaf is at the current position, the movement direction of the leaf maybe a first direction including one of the forward movement direction orthe backward movement direction as described elsewhere in the presentdisclosure (e.g., FIG. 6 and the descriptions thereof)). When the leafwas at the prior position, the movement direction of the leaf may changefrom a second direction (e.g., the forward movement direction or thebackward movement direction as described elsewhere in the presentdisclosure (e.g., FIG. 6 and the descriptions thereof)) to the firstdirection. For example, as shown in FIG. 11 , if the leaf is moving inthe forward movement direction, the current position of the leaf maycorrespond to a point on section (a) or section (d) of the movementcurve in FIG. 11 . The prior position of the leaf may correspond to thetransition point Tc. If the leaf is moving in the backward movementdirection, the current position of the leaf may correspond to a point onsection (b) or section (c) of the movement curve in FIG. 11 . The priorposition of the leaf may correspond to the transition point Ta. In someembodiments, the second main encoder value may be obtained from acomponent (e.g., the position feedback module 218) of the controlsystem, the storage device 130, the storage module 508, the storage unit610, or any other external storage.

In 808, a determination may be made as to whether the movement directionof the leaf moves in the backward movement direction. Operation 808 maybe performed by the offset determination unit 606. If it is determinedthat the movement direction of the leaf corresponding to the currentposition is the backward movement direction as described elsewhere inthe present disclosure, process 800 may proceed to operation 810. If itis determined that the movement direction of the leaf corresponding tothe current position is the forward movement direction as describedelsewhere in the present disclosure, process 800 may proceed tooperation 812.

In 810, a minimum value among the first reference offset value and thesum of a second reference offset value and the difference between thefirst main encoder value and the second main encoder value may bedesignated as an offset value of the leaf associated with the currentposition. Operation 810 may be performed by the offset determinationunit 606. The second reference offset value may correspond to the priorposition. In some embodiments, when the movement direction of the leafis the backward movement direction at the current position, the offsetvalue of the leaf may be determined according to Equation (2) below:Offset Px=min((Encoder Ta−Encoder Px+Offset Ta),Reference offset Px),  (2),where, Encoder Ta represents a main encoder value (e.g., the second mainencoder value) associated with a prior position of a leaf acquired by amain encoder of a driving component when the movement direction of theleaf changes from the forward movement direction to the backwardmovement direction, Encoder Px represents a main encoder value (e.g.,the first main encoder value) associated with a current position of theleaf acquired by the main encoder of the driving component, Offset Tadenotes the second reference offset value associated with the priorposition (e.g., transition point Ta as shown in FIG. 11 ) of the leaf,and Reference offset Px represents a first reference offset valueobtained from an offset table when the leaf is moving with the backwardmovement direction.

In 812, a maximum value among the first reference offset value and thesum of the second reference offset value and the difference between thefirst main encoder value and the second main encoder value may bedesignated as an offset value of the leaf associated with the currentposition. Operation 812 may be performed by the offset determinationunit 606. In some embodiments, when the movement direction of the leafis the forward movement direction at the current position, the offsetvalue of the leaf may be determined according to Equation (3) below:Offset Px=max((Encoder Tc−Encoder Px+Offset Tc),Reference offset Px),  (3),where Encoder T2 represents a main encoder value (e.g., the second mainencoder value) acquired by a main encoder of a driving componentassociated with a prior position of a leaf when the movement directionof the leaf changes from the backward movement direction to the forwardmovement direction, Encoder Px represents a main encoder value (e.g.,the first main encoder value) associated with a current position of theleaf acquired by the main encoder of the driving component, Offset Tcdenotes the second reference offset value associated with the priorposition (e.g., transition point Tc as shown in FIG. 11 )) of the leaf,and Reference offset Px represents a first reference offset valueobtained from an offset table when the leaf is moving with the forwardmovement direction.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure.

For example, operations 804 and 806 may be performed simultaneously orin a reverse order than that illustrated in FIG. 8 . As another example,process 800 may further include process a first signal associated withthe current position of the leaf acquired by the main encoder of thedriving component to obtain the first main encoder value. As stillanother example, process 800 may further include process a second signalassociated with the prior position of the leaf acquired by the mainencoder of the driving component to obtain the second main encodervalue.

FIG. 9 is a flowchart illustrating another exemplary process 900 fordetermining an offset value of a leaf according to some embodiments ofthe present disclosure. In some embodiments, one or more operations ofprocess 900 illustrated in FIG. 9 may be implemented in the radiotherapysystem 100 illustrated in FIG. 1 . For example, the process 900illustrated in FIG. 9 may be stored in the storage device 130 in theform of instructions, and invoked and/or executed by the processingdevice 120 (e.g., the processor 310 of the computing device 300 asillustrated in FIG. 3 , the GPU 430 or CPU 440 of the mobile device 400as illustrated in FIG. 4 ). Operation 706 may be performed by process900 as illustrated in FIG. 9 .

In 902, a current movement phase of a leaf corresponding to a currentposition of the leaf may be determined. Operation 902 may be performedby the movement determination unit 602. In some embodiments, the currentmovement phase of the leaf may be also referred to as a first movementphase when the leaf is at the current position (i.e., a first position).The current movement phase may be one of the four phases including afirst phase, a second phase, a third phase, and a fourth phase. The leafmay be determined in the first phase (also referred to as aforward-movement phase) when the leaf is moving toward the center of aradiation field. The leaf may be determined in the second phase (alsoreferred to as a backward consume phase) when the leaf is staticrelative to a carriage of an MLC including the leaf and configured tomove away from the center of the radiation field.

The leaf may be determined in the third phase (also referred to as abackward movement phase) when the leaf is moving away from the radiationfield. The leaf may be determined in the fourth phase (also referred toas a forward consume phase) when the leaf is static relative to thecarriage of the MLC including the leaf and configured to move toward thecenter of the radiation field. More descriptions of the four phases maybe found elsewhere in the present disclosure (e.g., FIG. 16A, and thedescriptions thereof).

In some embodiments, the movement determination unit 602 may determinethe current movement phase of the leaf based on measurements of a mainencoder (e.g., a motor encoder) of a driving component and/or anauxiliary encoder (e.g., a Hall sensor) associated with the leaf in twoadjacent sampling periods (also referred to as adjacent calculationcycles). As used herein, a measurement of each of the main encoderand/or the auxiliary encoder may include a count of signals acquired byeach of the main encoder and/or the second encoder which may be used todetermine a position of the leaf. Further, the current movement phase ofthe leaf may be determined based on a count difference of at least oneof the main encoder and/or the second encoder in two adjacent samplingperiods (also referred to as adjacent calculation cycles). For example,when the leaf is moving in the forward movement phase, if the countdifference between two measurements of the main encoder in adjacentsampling periods is less than a first threshold (e.g., −5, or a constantless than −5), the movement determination unit 602 may determine thatthe movement phase of the leaf changes and the leaf is moving into thebackward consume phase. If the count difference between two measurementsof the main encoder in adjacent sampling periods is greater than asecond threshold (e.g., −5, or a constant less than −5), the movementdetermination unit 602 may determine that the movement phase of the leafchanges and the leaf is moving into the forward consume phase.

As another example, when the movement phase of the leaf is unknown, ifthe count difference between the two measurements of the auxiliaryencoder in adjacent sampling periods is larger than a third threshold(e.g., 2, or a constant greater than 2), the movement determination unit602 may determine the current movement phase of the leaf as moving inthe forward movement phase. If the count difference between the twomeasurements of the auxiliary encoder in adjacent sampling periods isless than a fourth threshold (e.g., −2, or a constant less than −2), themovement determination unit 602 may determine the current movement phaseof the leaf as the backward movement phase.

As still another example, when the leaf is moving in the backwardconsume phase, if the count difference between the two measurements ofthe auxiliary encoder in adjacent sampling periods is larger than thefifth threshold (e.g. 0), the movement determination unit 602 maydetermine that the current movement phase of the leaf changes and theleaf is moving into the forward movement phase. If the count differencebetween the two measurements of the auxiliary encoder in adjacentsampling periods is less than the fifth threshold (e.g. 0), the movementdetermination unit 602 may determine that the current movement phase ofthe leaf changes and the leaf is moving into the backward movementphase. When the leaf is moving in the forward consume phase, if thecount difference between the two measurements of the auxiliary encoderin adjacent sampling periods is larger than the fifth threshold (e.g.0), the movement determination unit 602 may determine that the currentmovement phase of the leaf changes and the leaf is moving into theforward movement phase. If the count difference between the twomeasurements of the auxiliary encoder in adjacent sampling periods isless than the fifth threshold (e.g. 0), the movement determination unit602 may determine that the current movement phase of the leaf changesand the leaf is moving into the backward movement phase.

In 904, a reference offset value may be determined, which is associatedwith a prior position of the leaf at where a movement phase of the leafchanges from a prior movement phase to the current movement phase.Operation 904 may be performed by the offset determination unit 606. Asused herein, the prior position may be also referred to as a phasetransition position or transition point (e.g., transition points T1, T2,T3, and T4 as shown in FIG. 16A) of the leaf. The prior movement phasemay be also referred to as a second movement phase. The prior positionmay correspond to a transition point closest to the current position ofthe leaf. For example, if the current movement phase of the leafdetermined in 902 is the backward consume phase, the prior movementphase of the leaf may be the forward movement phase. Then the priorposition may correspond to a second transition point (e.g., transitionpoint T2 as shown in FIG. 16A) from the forward movement phase to thebackward consume phase. If the current movement phase of the leafdetermined in 902 is the backward movement phase, the prior the movementphase of the leaf may be the backward consume phase. Then the priorposition may correspond to a third transition point (e.g., transitionpoint T3 as shown in FIG. 16A) from the backward consume phase to thebackward movement phase.

If the current movement phase of the leaf determined in 902 is theforward movement phase, the prior movement phase of the leaf may be theforward consume phase. Then the prior position may correspond to a firsttransition point (e.g., transition point T1 as shown in FIG. 16A) fromthe forward consume phase to the forward movement phase. If the currentmovement phase of the leaf determined in 902 is the forward consumephase, and the prior movement phase of the leaf is the backward movementphase. Then the prior position may correspond to a fourth transitionpoint (e.g., transition point T4 as shown in FIG. 16A) from the backwardmovement phase to the forward consume phase.

The reference offset value of the leaf associated with the priorposition of the leaf may be an offset value when the leaf is moving atthe prior position. In some embodiments, if the leaf is in the forwardconsume phase, the reference offset value of the leaf may be equal to anoffset value corresponding to the fourth transition point (e.g.,transition point T4 as shown in FIG. 16A) from the backward movementphase to the forward consume phase. If the leaf is in the backwardconsume phase, the reference offset value of the leaf may be equal to anoffset value corresponding to the second transition point (e.g.,transition point T2 as shown in FIG. 16A) from the forward movementphase to the backward consume phase.

In 906, a first main encoder value acquired by a main encoder of adriving component associated with the leaf may be obtained, which isassociated with the current position of the leaf. Operation 906 may beperformed by the offset determination unit 606. In some embodiments, thefirst main encoder value may represent the current position of the leaf.In some embodiments, the first main encoder value may be obtained fromthe main encoder (e.g., the encoder 208) directly. In some embodiments,the first main encoder value may be obtained from the storage device130, the storage module 508, the storage unit 610, or any other externalstorage.

In 908, a second main encoder value acquired by the main encoder may beobtained, which is associated with the prior position of the leaf.Operation 908 may be performed by the offset determination unit 606. Insome embodiments, the second main encoder value acquired by the mainencoder may represent the prior position of the leaf. In someembodiments, the second main encoder value may be obtained from thestorage device 130, the storage module 508, the storage unit 610, or anyother external storage.

In 910, the offset value may be determined based on the reference offsetvalue and a difference between the first main encoder value and thesecond main encoder value. Operation 910 may be performed by the offsetdetermination unit 606.

In some embodiments, the offset value of the leaf associated with thecurrent position may be determined based on the reference offset valueand the difference between the first main encoder value and the secondmain encoder value. Further, the offset value of the leaf associatedwith the current position of the leaf may be equal to a sum between thereference offset value and the difference between the second mainencoder value and the first main encoder value as described by Equation(4) below:Offset Px=Encoder Tx−Encoder Px+Reference Offset Tx,  (4),where, Offset Tx represents an offset value corresponding to a currentposition of a leaf, Encoder Tx represents a main encoder valuecorresponding to a prior position when a movement phase of the leafchanges from a prior movement phase to a current movement phase, alsoreferred to as the second main encoder value For example, Encoder Tx maycorrespond to the transition position T2′ or T2 as shown in FIG. 19B.Encoder Px represents a main encoder value corresponding to the currentposition, also referred to as the first main encoder value, andReference Offset Tx represents a reference offset value corresponding tothe prior position. If the current movement phase of the leaf is thebackward consume phase, and the prior movement phase is the forwardmovement phase, the offset value (i.e., Offset Px) of the leafassociated with a current position in the backward consume phase may bedetermined as described by Equation (5) below:Offset Px=Encoder T2−Encoder Px+Reference Offset T2  (5),where Offset Px represents an offset value of the leaf associated with acurrent position in the backward consume phase, Encoder T2 represents amain encoder value acquired by the main encoder associated with aposition when the movement phase of the leaf changes from the forwardmovement phase to the backward consume phase, i.e., a second mainencoder value, and Encoder Px represents a main encoder value acquiredby the main encoder associated with the current position in the backwardconsume phase, i.e., a first main encoder value. Reference Offset T2represents a reference offset value of the second transition point T2that may be an offset value of the position when the movement phase ofthe leaf changes from the forward movement phase to the backward consumephase.

According to Equation (5), if the current position corresponds to thethird transition point when the movement phase of the leaf changes fromthe backward consume phase to the backward movement phase, the offsetvalue of the current position may be denoted by Equation (6):Offset Px=Offset T3=Encoder T2−Encoder T3+Offset T2  (6).

If the current movement phase of the leaf is the forward consume phase,and the prior movement phase is the backward movement phase, an offsetvalue (i.e., Offset Px) of the leaf associated with the current positionin the forward consume phase may be determined as described by Equation(7) below:Offset Px=Reference Offset T4−(Encoder Px−Encoder T4)  (7).where Offset Px represents an offset value of the leaf associated withthe current position in the forward consume phase, Encoder T4 representsa main encoder value (i.e., the second main encoder value) acquired bythe main encoder associated with a position when the movement phase ofthe leaf changes from the backward movement phase to the forward consumephase, Encoder Px represents a main encoder value (i.e., the first mainencoder value) acquired by the main encoder associated with the currentposition in the forward consume phase, and Reference Offset T4represents a reference offset value of the fourth transition point T4that may be an offset value of the position when the movement phase ofthe leaf changes from the backward movement phase to the forward consumephase.

According to Equation (7), if the current position includes the positionwhen the movement phase of the leaf changes from the forward consumephase to the forward movement phase, i.e., the first transition pointT1, the offset value of the current position may be denoted by Equation(8):Offset Px=Offset T1=(Encoder T4−Encoder T1+Offset T4)  (8).

In operation 912, the offset value of the current position of the leafmay be determined based on the reference offset value of the priorposition. Operation 912 may be performed by the offset determinationunit 606. When the leaf is at the prior position, a movement phase ofthe leaf changes from a prior movement phase to the current movementphase. The prior position may correspond to a transition point closestto the current position of the leaf. More descriptions for the priorposition of the leaf may be found in operation 904.

In some embodiments, if the leaf is in the forward movement phase or thebackward movement phase, a backlash between the leaf and the drivingcomponent may be unchanged, such that the offset value for removing thebacklash may be a constant. In other words, the offset value of the leafmay be unchanged when the leaf is moving in the forward movement phaseor the backward movement phase.

In some embodiments, if the leaf is in the forward movement phase, theoffset value of the current position may be equal to an offset value ofa phase transition position (e.g., first transition point T1 as shown inFIG. 16A) from the forward consume phase to the forward movement phase,denoted by offset T1, and may be equal to an offset value of a phasetransition position (e.g., second transition point T2 as shown in FIG.16A) from the forward movement phase to the backward consume direction,denoted by offset T2. In other words, the offset value of the currentposition in the forward movement phase may be denoted by OffsetPx=Offset T1=Offset T2.

In some embodiments, if the leaf is in the backward movement phase, theoffset value of the current position may be equal to an offset value ofa phase transition position (e.g., third transition point T3 as shown inFIG. 16A) from the backward consume phase to the backward movementphase, denoted by Offset T3, and may be also equal to an offset value ofa phase transition position (e.g., fourth transition point T4 as shownin FIG. 16A) from the backward movement phase to the forward consumephase, denoted by offset T4. In other words, the offset value of thecurrent position in the backward movement phase may be denoted by OffsetPx=Offset T3=Offset T4.

In some embodiments, if the angle of the leaf is 0 degree and the leafis in the forward movement phase, the offset value of the leaf may beequal to zero, which may be denoted by Offset Px=Offset T1=Offset T2=0.

In some embodiments, the angle of the leaf may change along with theleaf moves. The change of the angle of the leaf may cause a change ofbacklash error, and the offset value of the leaf needs to be modified.

If the angle of the leaf is about 0 degree, the angle change of the leafdoes not exceed a threshold, and the leaf is in the forward movementphase, the offset value of the current position in the forward movementphase may be equal to 0 that may be denoted by Offset Pr=OffsetT1=Offset T2=0. If the leaf is in the backward consume phase, the offsetvalue of the current position in the backward consume phase may bedenoted by Offset Px=Encoder T2−Encoder Px. If the leaf is in thebackward movement phase, the offset value of the current position in thebackward movement phase may denoted by Offset Px=Offset T3=OffsetT4=Encoder T2−Encoder T3. If the leaf is in the forward consume phase,the offset value of the current position in the forward consume phasemay denoted by Offset Px=(Encoder T2−Encoder T3)−(Encoder Px−EncoderT4).

If the angle change of the leaf exceeds a threshold, the offset value ofthe current position of the leaf may be determined based on thereference offset value of the prior position.

In some embodiments, if the leaf is in the forward movement phase or thebackward movement phase, whether the offset value of the currentposition needs to be modified may be determined by determining whetherthe angle change of the leaf exceeds the threshold. In some embodiments,if the leaf is in the forward movement phase or the backward movementphase, whether the offset value of the current position needs to bemodified may be determined based on measurements of a main encoder andan auxiliary encoder. More descriptions for determining whether theoffset value of the current position needs to be modified may be foundin FIG. 10 and the descriptions thereof.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. For example,process 900 may include the operation of obtaining the values acquiredby the Hall sensor. In some embodiments, operations 906 and 908 may beomitted. The offset value of the leaf associated with the currentposition may be equal to the reference offset value.

FIG. 10 is a flowchart illustrating an exemplary process 1000 fordetermining a reference offset value of a leaf according to someembodiments of the present disclosure. In some embodiments, one or moreoperations of process 1000 illustrated in FIG. 10 may be implemented inthe radiotherapy system 100 illustrated in FIG. 1 . For example, theprocess 1000 illustrated in FIG. 10 may be stored in the storage device130 in the form of instructions, and invoked and/or executed by theprocessing device 120 (e.g., the processor 310 of the computing device300 as illustrated in FIG. 3 , the GPU 430 or CPU 440 of the mobiledevice 400 as illustrated in FIG. 4 ). Operation 904 may be performedaccording to process 1000 as illustrated in FIG. 10 . According toprocess 1000, the offset value of a leaf may be influenced by the anglechange of the leaf moving in the forward movement phase or backwardmovement phase. However, in the forward consume phase or backwardconsume phase, the effect of the angle change of the leaf on the offsetvalue of a leaf may be neglected.

In 1002, a determination may be made to as whether an angle change of aleaf exceeds a threshold in a current movement phase. Operation 1002 maybe performed by the offset determination unit 606. If it is determinedthat the angle change of the leaf exceeds the threshold in the currentmovement phase, process 1000 may proceed to operation 1004. If it isdetermined that the angle change of the leaf does not exceed thethreshold in the current movement phase, process 1000 may proceed tooperation 1010.

For example, as shown in FIG. 198 , if the angle change of the leaf doesnot exceed a threshold in the forward movement phase, the offset valueof the leaf at the current position may be equal to the offset value ofthe transition point T1 i.e., Offset T1. If the angle change of the leafexceeds the threshold in the forward movement phase, a moving curve ofthe leaf in the forward movement phase may change from section (a) tosection (a)′, and the offset value of the leaf at the current positionneeds to be modified.

As another example, as shown in FIG. 19B, if the angle change of theleaf does not exceed a threshold in the backward movement phase, theoffset value of the leaf at the current position may be equal to theoffset value of the transition point T3 i.e., Offset T3. If the anglechange of the leaf exceeds the threshold in the backward movement phase,a moving curve of the leaf in the backward movement phase may changefrom section (c) to section (c)′, and the offset value of the leaf atthe current position needs to be modified.

In some embodiments, whether the angle change of the leaf exceeds thethreshold may be determined by determining whether an angle change valueof the leaf between a reference position and the current positionexceeds a threshold. Further, if the angle change value of the leafexceeds the threshold, the offset value of the leaf at the currentposition may be modified. For example, the angle change of the leaf maybe determined based on an angle change value of the leaf between theprior position and the current position. In some embodiments, whetherthe angle change of the leaf exceeds the threshold may be determined bydetermining whether an angle change value of the leaf at the currentposition with respect to a prior sampling period exceeds the threshold.

In some embodiments, the angle of the leaf may be determined accordingto Equation (1) as described in FIG. 7 . When the leaf is at thereference position Tr, the angle of the leaf may be α_(Tr). When theleaf is at the current position Px, the angle of the leaf may be α_(Px).The angle change value of the leaf may be denoted by Δα=α_(Px)−α_(Tr).Whether the angle change value Aa exceeds the threshold may bedetermined and the offset value of the leaf may be determined accordingto the determination that the angle change value Da exceeds thethreshold.

In some embodiments, whether the angle change of the leaf exceeds thethreshold may be determined based on measurements of a main encoder of adriving component and an auxiliary encoder associated with the currentposition of the leaf and measurements of a main encoder of a drivingcomponent and an auxiliary encoder associated with the referenceposition of the leaf. For example, if the main encoder includes a motorencoder and the auxiliary encoder includes a Hall sensor, whether theangle change of the leaf exceeds the threshold may be determined basedon a change of a measurement Encoder Px of the motor encoder (or themain encoder) associated with the current position Px with respect to ameasurement of the motor encoder (or the main encoder) associated withthe reference position Tr and a change of a measurement Hall Px of theHall sensor (or the auxiliary encoder) associated with the currentposition Px with respect to a measurement of the Hall sensor (or theauxiliary encoder) associated with the reference position Tr. Thereference position may include a phase transition position, a positionin a prior sampling period, a position between the phase transitionposition and the position in a prior sampling period, etc.

For example, a first main encoder value and a first auxiliary encodervalue of the current position of the leaf may be obtained. The firstmain encoder value may be acquired by the main encoder when the leaf isat the current position and the first auxiliary encoder value may beacquired by the auxiliary encoder when the leaf is at the currentposition. A second main encoder value and a second auxiliary encodervalue of the phase transition position of the leaf may be obtained. Thesecond main encoder value may be acquired by the main encoder when theleaf is at the phase transition position and the second auxiliaryencoder value may be acquired by the auxiliary encoder when the leaf isat the phase transition position. A first difference between the firstmain encoder value and the second main encoder value. A seconddifference between the first auxiliary encoder value and the secondauxiliary encoder value. Whether the offset value of the leaf needs tobe modified may be determined based on the first difference and thesecond difference.

For example, whether the offset value of the leaf needs to be modifiedmay be determined based on a difference between the first difference andthe second difference or a ratio of the first difference and the seconddifference. If the difference between the first difference and thesecond difference or the ratio of the first difference and the seconddifference exceeds a threshold, the angle change of the leaf exceeds thecorresponding threshold and the offset value of the leaf needs to bemodified may be determined. If the difference between the firstdifference and the second difference or the ratio of the firstdifference and the second difference does not exceed the threshold, theangle change of the leaf does not exceed the corresponding threshold andthe offset value of the leaf does not need to be modified may bedetermined.

In 1004, an offset value associated with a reference position in thecurrent movement phase may be determined. Operation 1004 may beperformed by the offset determination unit 606. The reference positionmay be a specific position in the current movement phase. For example,the reference position may be a phase transition position from a priormovement phase to the current movement phase. As another example, thereference position may be a position in a prior sampling period. Asstill another example, the reference position may be a position betweenthe phase transition position and the position in the prior samplingperiod.

If the leaf is in the forward movement phase, the offset value of thereference position may be equal to Offset T1. If the leaf is in thebackward movement phase, the offset value of the reference position maybe equal to Offset T3.

In 1006, measurement values of the main encoder and the auxiliaryencoder may be obtained when the leaf is at the current position and thereference position respectively. Operation 1006 may be performed by theoffset determination unit 606.

In some embodiments, the main encoder may be a motor encoder. Theauxiliary encoder may be a Hall sensor. A first motor encoder valueEncoder Px and a first Hall value Hall Px corresponding to the currentposition Px may be obtained. The first motor encoder value Encoder Pxmay be acquired by the motor encoder and the first Hall value Hall Pxmay be acquired by the Hall sensor. A second motor encoder value EncoderTr and a second Hall value Hall Tr corresponding to the referenceposition Tr may be obtained. The second motor encoder value Encoder Trmay be acquired by the motor encoder and the second Hall value Hall Trmay be acquired by the Hall sensor. In some embodiments, the first motorencoder value Encoder Px, the first Hall value Hall Px, the second motorencoder value Encoder Tr, and the second Hall value Hall Tr may beobtained from the storage device 130, the storage module 508, thestorage unit 610 or any other storage device.

In 1008, the offset value associated with the current position of theleaf may be determined based on the offset value of the referenceposition and the measurement values of the main encoder and theauxiliary encoder corresponding to the current position and thereference position respectively. Operation 1008 may be performed by theoffset determination unit 606. As used herein, the second first idealreference offset value associated with the prior position may also referto as a reference offset value associated with the prior position notincluding the error caused by the Hall sensor.

For example, the main encoder may be a motor encoder. The auxiliaryencoder may be a Hall sensor. When the leaf is at the referenceposition, the offset value of the leaf at the reference position may bedetermined based on measurement values of the motor encoder and the Hallsensor according to Equation (9):Offset Tr=(Hall Tr−δ)−Encoder Tr  (9),where Offset Tr refers to an offset value of the leaf at the referenceposition Tr, Hall Tr refers to a measurement value of the Hall sensorwhen the leaf is at the reference position, i.e., the second Hall value,Encoder Tr refers to a measurement value of the motor encoder when theleaf is at the reference position, i.e., the second motor encoder value,and S refers to a feedback error of the Hall sensor caused by poorlinearity and repeatability of the Hall sensor.

When the leaf is at the current position, the offset value of the leafat the current position may be determined based on measurement values ofthe motor encoder and the Hall sensor according to Equation (10):Offset Px=(Hall Px−δ)−Encoder Px  (10),where Offset Px refers to an offset value of the leaf at the currentposition Px, Hall Px refers to a measurement value of the Hall sensorwhen the leaf is at the current position, i.e., the first Hall value,Encoder Px refers to a measurement value of the motor encoder when theleaf is at the current position, i.e., the first motor encoder value,and S refers to the feedback error of the Hall sensor caused by poorlinearity and repeatability of the Hall sensor.

According to Equations (9) and (10), the offset value of the leaf at thecurrent position may be determined according to Equation (11):Offset Px=Offset Tr+(Hall Px−Hall Tr)−(Encoder Px−Encoder Tr)  (11).

If the leaf is in the forward movement phase, the offset value of thereference position Offset Tr may be equal to Offset T1. If the leaf isin the backward movement phase, the offset value of the referenceposition Offset Tr may be equal to Offset T3.

According to Equation (11), the feedback error of the Hall sensor may beremoved.

In 1010, an offset value of the leaf at a prior position may bedetermined as the offset value of the leaf at the current position.Operation 1010 may be performed by the offset determination unit 606.More descriptions for determining the offset value of the leaf at theprior position may be found in FIG. 9 and the descriptions thereof.

FIG. 11 is a schematic diagram illustrating an exemplary movement curveof a leaf according to some embodiments of the present disclosure. Themovement curve of the leaf may be obtained when the leaf has an angle of0 degrees as shown in FIG. 14C, also referred to that the leaf isparallel to the horizontal plane. As illustrated in FIG. 11 , thehorizontal axis (i.e., X-axis) represents a position of the leafacquired by a main encoder associated with the leaf. The vertical axis(i.e., Y-axis) represents the accurate position of the leaf acquired bya distance measurement device, for example, a laser sensor. The solidline denotes that the leaf is moving along the backward movementdirection, i.e., moving away from the center of a radiation field. Thedotted line denotes that the leaf is moving along the forward movementdirection, i.e., moving toward the center of the radiation field. Thus,two transition points associated with the movement direction of the leafare shown in FIG. 11 . Ta represents the transition point from theforward movement direction to the backward movement direction. Tcrepresents the transition point from the backward movement direction tothe forward movement direction. The movement curve of the leaf includesfour sections corresponding to four movement phases of the leafrespectively. Section (a) corresponds to a first phase (also referred toas the forward movement phase) of the leaf that the leaf is movingtoward the center of the radiation field. Section (b) corresponds to asecond phase (also referred to as backward consume phase) that the leafis static relative to a carriage of an MLC and configured to move awayfrom the center of the radiation field. Section (c) corresponds to athird phase (also referred to as the backward movement phase) that theleaf is moving away from the center of a radiation field. And section(d) corresponds to a fourth phase (also referred to as forward consumephase) that the leaf is static relative to the carriage of the MLC andconfigured to move toward the center of the radiation field.

FIG. 12 is a schematic diagram illustrating an exemplary movement curveof a leaf according to some embodiments of the present disclosure. Themovement curve of the leaf is obtained when the leaf is located upward amotor associated with the leaf (e.g., the leaf 1442 with an angle of 90degrees as shown in FIG. 14B). As shown in FIG. 12 , section (a) of themovement curve in FIG. 11 shifts to section (a′) causing the shorteningof section (b) and section (d), as well as the shifting of thetransition point from Ta to Ta′.

FIG. 13 is a schematic diagram illustrating another exemplary movementcurve of a leaf according to some embodiments of the present disclosure.The movement curve of the leaf is obtained when the leaf is locateddownward a motor associated with the leaf (e.g., the leaf 1444 with anangle of −90 degrees as shown in FIG. 14B). As shown in FIG. 13 ,section (c) of the movement curve in FIG. 11 shifts to section (c′)causing the shortening of section (b) and section (d), as well as theshifting of the transition point from Tc to Tc′.

FIG. 14A is a schematic diagram illustrating an exemplary gantry of theradiotherapy device 110 in a sectional view according to someembodiments of the present disclosure. In FIG. 14A, a gantry 1420 mayinclude a collimator 1440. An MLC may be mounted on the collimator 1440and rotate along the collimator 1440. The angle of the gantry (gantryangle) is 90 degrees relative to the horizontal plane as described by aplane formed by X-axis and Y-axis. Z-axis denotes a vertical direction.The direction denoted by arrow “a” corresponds to a direction toward thecollimator 1440. Along the direction denoted by the arrow “a”, thecollimator 1440 may be arranged in different angles relative to thehorizontal plane, for example, 90 degrees, 0 degrees, etc.

FIG. 14B and FIG. 14C are schematic diagrams illustrating exemplaryleaves of the multi-leaf collimator 1440 in a sectional view accordingto some embodiments of the present disclosure. As shown in FIG. 14B, theangle of the gantry 1420 is 90 degrees relative to the horizontal plane.The angle of the collimator 1440 is 0 degrees relative to the horizontalplane. Then, the leaf 1442 and the leaf 1444 are vertical to thehorizontal plane. The leaf 1442 has an angle of 90 degrees. The leaf1444 has an angle of −90 degrees. As shown in FIG. 14C, the angle of thecollimator 1440 is 90 degrees relative to the horizontal plane, and theleaf 1442 and the leaf 1444 are parallel to the horizontal plane. Theangle of the leaf 1442 and the leaf 1444 may be determined based on theangle of the collimator 1440 and the angle of the gantry 1420 accordingto Equation (1) as described in FIG. 7 .

FIG. 15 is a schematic diagram illustrating an exemplary relationshipbetween the angle of a leaf and movement curve of the leaf according tosome embodiments of the present disclosure. The angle of a leaf (alsoreferred to as leaf angle) may range from −180 degree to 180 degrees.According to large amounts of experiments, the movement curve of theleaf is distributed according to the leaf angle. The movement curves ofthe leaf with a leaf angle in the range of 0 degrees and 90 degrees aresimilar to that of the leaf with a leaf angle in the range of 90 degreesto 180 degrees. The movement curves of the leaf with a leaf angle in therange from 0 degrees to −90 degree are similar to that of the leaf witha leaf angle in the range from −90 degree to −180 degree. In a firstrange between −90 degree and −10 degree, the movement curves of the leafare similar to the movement curve with the leaf angle of −90 degree,which means the backlash errors of the leaf with a leaf angle in thefirst range are approximately equal to the backlash error when the leafangle is −90 degree. In a second range between −10 degree and 10 degree,the movement curves of the leaf are similar to the movement curve withthe leaf angle of 0 degree, which means the backlash errors of the leafwith a leaf angle in the second range are approximately equal to thebacklash error when the leaf angle is 0 degree. In a third range between10 degree and 90 degree, the movement curves of the leaf are similar tothe movement curve with the leaf angle of 90 degree, which means thebacklash errors of the leaf with a leaf angle in the third range areapproximately equal to the backlash error when the angle of the leaf is90 degree.

FIG. 16 is a schematic diagram illustrating an exemplary movement curveof a leaf according to some embodiments of the present disclosure. Themovement curve of the leaf may be obtained when the leaf has an angle of0 degrees. The horizontal axis (i.e., X-axis) shows a position of theleaf which means the position of the leaf being acquired by a mainencoder associated with the leaf. The vertical axis (i.e., Y-axis) showsa Hall position of the leaf which means the position of the leaf beingacquired by a Hall sensor associated with the leaf. The solid linedenotes that the leaf moves away from the center of a radiation field(i.e., the backward movement direction). The dotted line denotes thatthe leaf moves toward the center of the radiation field (i.e., theforward movement direction). As shown in FIG. 16 , the movement curve ofthe leaf includes four sections corresponding to four movement phases ofthe leaf respectively. Section (a) corresponds to a first phase (alsoreferred to as the forward movement phase) of the leaf that the leaf ismoving toward the center of the radiation field. Section (b) correspondsto a second phase (also referred to as backward consume phase) that theleaf is static relative to a carriage of an MLC and configured to moveaway from the center of the radiation field. Section (c) corresponds toa third phase (also referred to as the backward movement phase) that theleaf is moving away from the center of the radiation field. And section(d) corresponds to a fourth phase (also referred to as forward consumephase) that the leaf is static relative to the carriage of the MLC andconfigured to move toward the center of the radiation field. Thus, fourtransition points associated with four movement phases are shown in FIG.16 . T1 represents a first transition point from the forwarding consumephase to the forward movement phase. T2 represents a second transitionpoint from forward movement phase to the backward consume phase. T3represents a third transition point from the backward consume phase tothe backward movement phase. And T4 represents a fourth transition pointfrom the forward consuming phase to the forward movement phase.

FIG. 17 is a schematic diagram illustrating exemplary movement phases aleaf according to some embodiments of the present disclosure. As shown,exemplary movement phases of a leaf may include a forward movement phase1704, a backward movement phase 1706, a backward consume phase 1708, anda forward consume phase 1710 as described elsewhere in the presentdisclosure (e.g., FIG. 9 and FIG. 16 , and the descriptions thereof). Aninitial phase of the leaf is unknown corresponding to an initialposition of the leaf. The movement phases of the leaf may be determinedbased on a count difference of a Hall sensor and/or an encoderassociated with the leaf between two adjacent calculation cycles, suchas kth and (k−1)th. For example, the leaf is determined in the forwardmovement phase 1704 if a count difference of a Hall sensor associatedwith the leaf between two adjacent calculation cycles (i.e., Δhall=hall(k)−hall (k−1)) is greater than 2 counts. If the count difference Δhallis less than −2 counts, the leaf is in the backward movement phase 1706.When the leaf is in the forward movement phase 1704, the movement phaseof the leaf changes from the forward movement phase 1704 to the backwardconsume phase 1708 if a count difference of an encoder associated withthe leaf between two adjacent calculation cycles (i.e.,Δenc=enc(k)−enc(k−1)) is less than −5. When the leaf is in the backwardmovement phase 1706, the movement phase of the leaf changes from thebackward movement phase 1706 to the forward consume phase 1710 if thecount difference Δenc is greater than 5 counts.

When the leaf is in the backward consume phase 1708, the movement phaseof the leaf changes from the backward consume phase 1708 to the forwardmovement phase 1704 if the count difference Δhall is greater than 0counts. On the contrary, the leaf gets into the backward movement phase1706 with the count difference Δhall less than 0 counts. When the leafis in the forward consume phase 1710, the movement phase of the leafchanges from the forward consume phase 1710 to the forward movementphase 1704 if the count difference Δhall is greater than 0 counts. Onthe contrary, the leaf gets into the backward movement phase 1706 withthe count difference Δhall less than 0 counts.

FIG. 18A is a schematic illustrating an exemplary angle relationshipbetween a leaf, collimator, and gantry according to some embodiments ofthe present disclosure. The leaf moves with the rotation of a gantry1820 and a collimator 1840. As shown in FIG. 18A, an angle of thecollimator 1840 is 0 degrees relative to the horizontal plane describedby a plane formed by X-axis and Y-axis, which is as same as the angle ofthe gantry 1820. Z-axis denotes a vertical direction. The angle of theleaf 1842 and the leaf 1844 are determined as 0 degrees relative to thehorizontal plane based on the angle of the collimator 1804 and the angleof the gantry 1820 according to Equation (1) as described in FIG. 7 .

FIGS. 18B-18E are schematics illustrating exemplary backlash error of amulti-leaf collimator (MLC) according to some embodiments of the presentdisclosure. A leaf may be driven by a driving component including a ballscrew and a motor (not shown). The ball screw may include a screw 1860and a nut 1880. The screw 1860 and the nut 1880 may be configured with aplurality of teeth (e.g., a screw tooth 1862 on the screw 1860 and a nuttooth 1882 on the nut 1880). The backlash error may exist between thetwo teeth on the screw 1860 and the nut 1880 respectively when the motorchanges rotation direction. FIGS. 18B-18E show backlash errors relatingto the driving component of the leaf corresponding to the four movementphases as described elsewhere in the present disclosure (e.g., FIG.16A).

As shown in FIG. 18B, the leaf is in the forward movement phase drivenby the motor associated with the leaf. Two teeth (e.g., the screw tooth1862 and the nut tooth 1882) on the screw 1860 and the nut 1840respectively are contacted by each other. There is no backlash betweenthe two teeth (e.g., the screw tooth 1862 and the nut tooth 1882) on thescrew 1860 and the nut 1880 respectively.

As shown in FIG. 18C, the motor changes the rotation direction and theleaf is in the backward consume phase. There is a backlash error (e.g.,distance d1) between two teeth (e.g., the screw tooth 1862 and the nuttooth 1884 adjacent to the nut tooth 1882) on the screw 1860 and the nut1880 respectively.

As shown in FIG. 18D, the leaf is in the backward movement phase drivenby the motor associated with the leaf. Two teeth (e.g., the screw tooth1862 and the nut tooth 1884) on the screw 1860 and the nut 1880respectively are contacted by each other. There is no backlash betweenthe two teeth (e.g., the screw tooth 1862 and the nut tooth 1884adjacent to the nut tooth 1882) on the screw 1860 and the nut 1880respectively.

As shown in FIG. 18E, the motor changes the rotation direction and theleaf is in the forward consume phase. There is a backlash error (e.g.,distance d2) between two teeth (e.g., the screw tooth 1862 and the nuttooth 1882) on the screw 1860 and the nut 1880 respectively.

FIG. 19A is a schematic illustrating an exemplary angle relationshipbetween a leaf, collimator, and gantry according to some embodiments ofthe present disclosure. The leaf moves with the rotation of a gantry anda collimator 1920. As shown in FIG. 19A, an angle of the collimator 1920is 0 degrees relative to the horizontal plane, which is perpendicular tothe gantry 1802. The angle of the leaf is determined as 90 degreesrelative to the horizontal plane based on the angle of the collimator1920 and the angle of the gantry according to Equation (1) as describedin FIG. 7 .

FIG. 19B is a schematic diagram illustrating an exemplary movement curveof a leaf described in FIG. 19A according to some embodiments of thepresent disclosure. When an angle of the leaf changes from 0 degrees to90 degrees in the forward movement phase, the movement curve of the leafcorresponding to the forward movement phase moves from section (a) tosection (a)′. The second transition point T2 also moves to point T2′.When an angle of the leaf changes from 0 degrees to −90 degrees in thebackward movement phase, the movement curve of the leaf corresponding tothe backward movement phase moves from section (c) to section (c)′. Thethird transition point T3 also moves to point T3′.

Moreover, certain terminology has been used to describe embodiments ofthe present disclosure. For example, the terms “one embodiment,” “anembodiment,” and/or “some embodiments” mean that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the present disclosure.

Further, it will be appreciated by one skilled in the art, aspects ofthe present disclosure may be illustrated and described herein in any ofa number of patentable classes or context including any new and usefulprocess, machine, manufacture, or composition of matter, or any new anduseful improvement thereof. Accordingly, aspects of the presentdisclosure may be implemented entirely hardware, entirely software(including firmware, resident software, micro-code, etc.) or combiningsoftware and hardware implementation that may all generally be referredto herein as a “unit,” “module,” or “system.” Furthermore, aspects ofthe present disclosure may take the form of a computer program productembodied in one or more computer readable media having computer readableprogram code embodied thereon.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including electro-magnetic, optical, or thelike, or any suitable combination thereof. A computer readable signalmedium may be any computer readable medium that is not a computerreadable storage medium and that may communicate, propagate, ortransport a program for use by or in connection with an instructionexecution system, apparatus, or device. Program code embodied on acomputer readable signal medium may be transmitted using any appropriatemedium, including wireless, wireline, optical fiber cable, RF, or thelike, or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in a combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB. NET,Python or the like, conventional procedural programming languages, suchas the “C” programming language, Visual Basic, Fortran 2103, Perl, COBOL2102, PHP, ABAP, dynamic programming languages such as Python, Ruby andGroovy, or other programming languages.

The program code may execute entirely on the user's computer, partly onthe user's computer, as a stand-alone software package, partly on theuser's computer and partly on a remote computer or entirely on theremote computer or server. In the latter scenario, the remote computermay be connected to the user's computer through any type of network,including a local area network (LAN) or a wide area network (WAN), orthe connection may be made to an external computer (for example, throughthe Internet using an Internet Service Provider) or in a cloud computingenvironment or offered as a service such as a Software as a Service(SaaS).

Furthermore, the recited order of processing elements or sequences, orthe use of numbers, letters, or other designations, therefore, is notintended to limit the claimed processes and methods to any order exceptas may be specified in the claims. Although the above disclosurediscusses through various examples what is currently considered to be avariety of useful embodiments of the disclosure, it is to be understoodthat such detail is solely for that purpose and that the appended claimsare not limited to the disclosed embodiments, but, on the contrary, areintended to cover modifications and equivalent arrangements that arewithin the spirit and scope of the disclosed embodiments. For example,although the implementation of various components described above may beembodied in a hardware device, it may also be implemented as a softwareonly solution, for example, an installation on an existing server ormobile device.

Similarly, it should be appreciated that in the foregoing description ofembodiments of the present disclosure, various features are sometimesgrouped in a single embodiment, figure, or description thereof for thepurpose of streamlining the disclosure aiding in the understanding ofone or more of the various inventive embodiments. This method ofdisclosure, however, is not to be interpreted as reflecting an intentionthat the claimed subject matter requires more features than areexpressly recited in each claim. Rather, inventive embodiments lie inless than all features of a single foregoing disclosed embodiment.

In some embodiments, the numbers expressing quantities or propertiesused to describe and claim certain embodiments of the application are tobe understood as being modified in some instances by the term “about,”“approximate,” or “substantially.” For example, “about,” “approximate,”or “substantially” may indicate ±20% variation of the value itdescribes, unless otherwise stated. Accordingly, in some embodiments,the numerical parameters set forth in the written description andattached claims are approximations that may vary depending upon thedesired properties sought to be obtained by a particular embodiment. Insome embodiments, the numerical parameters should be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques. Notwithstanding that the numerical ranges andparameters setting forth the broad scope of some embodiments of theapplication are approximations, the numerical values set forth in thespecific examples are reported as precisely as practicable.

Each of the patents, patent applications, publications of patentapplications, and other material, such as articles, books,specifications, publications, documents, things, and/or the like,referenced herein is hereby incorporated herein by this reference in itsentirety for all purposes, excepting any prosecution file historyassociated with same, any of same that is inconsistent with or inconflict with the present document, or any of same that may have alimiting affect as to the broadest scope of the claims now or laterassociated with the present document. By way of example, should there beany inconsistency or conflict between the description, definition,and/or the use of a term associated with any of the incorporatedmaterial and that associated with the present document, the description,definition, and/or the use of the term in the present document shallprevail.

In closing, it is to be understood that the embodiments of theapplication disclosed herein are illustrative of the principles of theembodiments of the application. Other modifications that may be employedmay be within the scope of the application. Thus, by way of example, butnot of limitation, alternative configurations of the embodiments of theapplication may be utilized in accordance with the teachings herein.Accordingly, embodiments of the present application are not limited tothat precisely as shown and described.

We claim:
 1. A method implemented on a computing device having at leastone processor and at least one computer-readable storage medium forcorrecting position errors for a multi-leaf collimator (MLC), the MLCincluding a plurality of leaves to shape a radiation field, each of theplurality of leaves being associated with a driving component includinga main encoder, the method comprising: determining a first position fora leaf of the plurality of leaves; determining at least one of a firstmovement direction or a first angle of the leaf at the first position,wherein a movement of the leaf along the first movement direction isconfigured to move toward or away from a center of the radiation field,and the first angle of the leaf is determined by: obtaining an angle ofa gantry corresponding to the first position of the leaf; obtaining anangle of a collimator corresponding to the first position of the leaf,wherein the MLC is mounted in the collimator and rotates along with thecollimator; and determining the first angle of the leaf based on theangle of the gantry and the angle of the collimator; determining anoffset value associated with the first position based on at least one ofthe first angle or the first movement direction; and determining atarget position of the leaf based on the offset value.
 2. The method ofclaim 1, wherein the first movement direction is determined by:obtaining a first velocity relating to the driving component; inresponse to a determination that the first velocity relating to thedriving component is lower than a first threshold, determining the firstmovement direction as a backward movement direction, the leaf beingconfigured to move away from the center of the radiation field along thebackward movement direction; and in response to a determination that thefirst velocity relating to the driving component is greater than asecond threshold, determining the first movement direction as a forwardmovement direction, the leaf being configured to move toward the centerof the radiation field along the forward movement direction.
 3. Themethod of claim 1, wherein the determining a target position of the leafbased on the offset value includes: subtracting the offset value from apreprogrammed position of the leaf.
 4. The method of claim 1, whereinthe determining an offset value associated with the first position basedon at least one of the first angle or the first movement directionincludes: obtaining a first reference offset value associated with thefirst position of the leaf from a pre-determined offset table based onat least one of the first angle or the first movement direction;obtaining a first main encoder value corresponding to the first positionof the leaf, the first main encoder value being acquired by the mainencoder; obtaining a second main encoder value corresponding to a secondposition of the leaf, the second main encoder value being acquired bythe main encoder, and the second position being a position at where amovement direction of the leaf changes from a second movement directionto the first movement direction; and determining the offset valueassociated with the first position based on the first movementdirection, the first reference offset value, and a difference betweenthe first main encoder value and the second main encoder value.
 5. Themethod of claim 4, wherein the determining the offset value associatedwith the first position based on the first movement direction, the firstreference offset value, and a difference between the first main encodervalue and the second main encoder value includes: if the leaf moves awayfrom the center of the radiation field along the first movementdirection, designating a minimum value among the first reference offsetvalue and a sum of a second reference offset value associated with thesecond position and the difference between the first main encoder valueand the second main encoder value as the offset value associated withthe first position; and if the leaf moves toward the center of theradiation field along the first movement direction, designating amaximum value among the first reference offset value and a sum of thesecond reference offset value associated with the second position andthe difference between the first main encoder value and the second mainencoder value as the offset value associated with the first position. 6.The method of claim 1, wherein the determining an offset valueassociated with the first position based on at least one of the firstangle or the first movement direction includes: if the leaf moves towardthe center of the radiation field along the first movement direction andthe first angle is equal to 0 degrees, designating the offset valueassociated with the first position as
 0. 7. The method of claim 1,wherein the determining a target position of the leaf based on theoffset value includes: obtaining a first main encoder valuecorresponding to the first position of the leaf acquired by the mainencoder; and correcting the first main encoder value based on the offsetvalue to obtain the target position of the leaf.
 8. The method of claim7, wherein the correcting the first main encoder value based on theoffset value includes: adding the offset value to the first main encodervalue to obtain the target position of the leaf.
 9. A method implementedon a computing device having at least one processor and at least onecomputer-readable storage medium for correcting position errors for amulti-leaf collimator (MLC), the MLC including a plurality of leaves toshape a radiation field, each of the plurality of leaves beingassociated with a driving component including a main encoder, the methodcomprising: determining a first position for a leaf of the plurality ofleaves; determining a first movement phase of the leaf at the firstposition, wherein the leaf in the first movement phase is configured tomove toward or away from a center of the radiation field; determining anoffset value associated with the first position based on a determinationwhether the leaf in the first movement phase moves toward or away from acenter of the radiation field; and determining a target position of theleaf based on the offset value; wherein the first movement phase of theleaf at the first position is determined based on a difference between afirst measurement value and a second measurement value acquired by atleast one of the main encoder or an auxiliary encoder in two samplingperiods.
 10. The method of claim 9, wherein the first movement phaseincludes one of: a first phase in which the leaf is moving toward thecenter of the radiation field; a second phase in which the leaf isstatic relative to a carriage of the MLC and is directed to move awayfrom the center of the radiation field; a third phase in which the leafis moving away from the center of the radiation field; and a fourthphase in which the leaf is static relative to the carriage of the MLCand is directed to move toward the center of the radiation field. 11.The method of claim 10, wherein the determining an offset valueassociated with the first position based on the first movement phaseincludes: in response to a determination that the first movement phaseis the second phase or the fourth phase, determining a reference offsetvalue associated with a second position of the leaf, the second positioncorresponding to a position at where a movement phase of the leafchanges from a second movement phase to the first movement phase;obtaining a first main encoder value corresponding to the first positionof the leaf, the first main encoder value being acquired by the mainencoder; obtaining a second main encoder value corresponding to thesecond position of the leaf, the second main encoder value beingacquired by the main encoder; and determining the offset valueassociated with the first position based on a difference between thefirst main encoder value and the second main encoder value and thereference offset value associated with the second position.
 12. Themethod of claim 10, wherein the determining an offset value associatedwith the first position based on the first movement phase includes: inresponse to a determination that the first movement phase is the firstphase or the third phase, the offset value associated with the firstposition is constant.
 13. The method of claim 12, wherein the offsetvalue associated with the first position is equal to a reference offsetvalue associated with a second position at where a movement phase of theleaf changes from a second movement phase to the first movement phase.14. The method of claim 13, further comprising: determining whether anangle change value of the leaf between angles of the leaf at the firstposition and the second position exceeds a preprogrammed threshold; andin response to a determination that the angle change value exceeds thepreprogrammed threshold, correcting the offset value associated with thefirst position of the leaf.
 15. The method of claim 13, furthercomprising: obtaining a first main encoder value and a first auxiliaryencoder value corresponding to the first position of the each of theplurality of leaves, the first main encoder value being acquired by themain encoder, the first auxiliary encoder value being acquired by theauxiliary encoder; obtaining a second main encoder value and a secondauxiliary encoder value corresponding to the second position, the secondmain encoder value being acquired by the main encoder, the secondauxiliary encoder value being acquired by the auxiliary encoder;determining a first difference between the first main encoder value andthe second main encoder value; determining a second difference betweenthe first auxiliary encoder value and the second auxiliary encodervalue; determining whether the offset value associated with the firstposition needs to be corrected based on the first difference and thesecond difference; and correcting the offset value associated with thefirst position of the leaf.
 16. The method of claim 14, wherein one ofthe angles of the leaf is determined by: obtaining an angle of a gantrycorresponding to the first position of the leaf; obtaining an angle of acollimator corresponding to the first position of the leaf, wherein theMLC is mounted in the collimator and rotates along with the collimator;and determining the angle of the leaf based on the angle of the gantryand the angle of the collimator.
 17. The method of claim 10, wherein ifthe first movement phase is the first phase and an angle of the leaf atthe first position is equal to 0 degrees, the offset value associatedwith the first position is equal to
 0. 18. The method of claim 9,wherein the determining a target position of the leaf based on theoffset value includes: subtracting the offset value from a preprogrammedposition of the leaf.
 19. A system for correcting position errors for amulti-leaf collimator (MLC), the MLC including a plurality of leaves toshape a radiation field, each of the plurality of leaves beingassociated with a driving component including a main encoder, the systemcomprising: at least one storage device storing executable instructions,and at least one processor in communication with the at least onestorage device, when executing the executable instructions, causing thesystem to: determine a first position for a leaf of the plurality ofleaves; determine at least one of a first movement direction or a firstangle of the leaf at the first position, wherein a movement of the leafalong the first movement direction is configured to move toward or awayfrom a center of the radiation field, and the first angle of the leaf isdetermined by: obtaining an angle of a gantry corresponding to the firstposition of the leaf; obtaining an angle of a collimator correspondingto the first position of the leaf, wherein the MLC is mounted in thecollimator and rotates along with the collimator; and determining thefirst angle of the leaf based on the angle of the gantry and the angleof the collimator; determine an offset value associated with the firstposition based on at least one of the first angle or the first movementdirection; and determine a target position of the leaf based on theoffset value.
 20. The method of claim 9, wherein the two samplingperiods are two adjacent sampling periods, the first measurement valuecorresponds to the first position, and the auxiliary encoder isassociated with the leaf and configured to determine a position of theleaf.